Sir John Marshall has an extensive section (see Images 2 and 3 for his references) on linga, yoni and the often difficult job of distinguishing them from game pieces and stones in general (Mohenjo-daro, p. 58-63). We reproduce the entire section from Marshall below, and Images 2 and 3 have some of the examples he refers to by number. In short, naming objects across millennia is imprecise at best.

"PHALLIC AND BAETYLIC STONES
"With these parenthetical remarks about Saktism, we may now return to consider the phallic emblems -the yoni and linga- which were to become so characteristic of Saivism, and with them also the worship of baetylic stones, between which and phallic emblems ti is frequently difficult to distinguish. [footnote: Cf. Crooke, op. cit., p. 319.]

"In India the reverence paid to stones is as universal as it is ancient. Primarily stones were worshipped because of their peculiar appearance or some weird or uncanny feature that distinguished them from other Stones; then, in the animistic stage, they came to be regarded as the habitation of a spirit; and eventually, with the development of iconism, they took shape as idols. Even to-day, however, the worship of aniconic stones, both natural and worked, plays an important rôle. They serve as watchmen [footnote: Muthiya deo (the divine watchman) is a common name of the stone of the cross-roads; bhainsasur (the buffalo god) of the guardian stone ni the fields. Cf. Crooke, ERE. xi, p. 872.] of the cross-roads; they guard the villages and fields from evil spirits; they ensure good crops and avert or cure diseases among men and cattle ; in birth and marriage rites they have a very special place; and they provide a resting place for the spirit of the departed. In the shape of the salagrama [footnote: For the salagrama stone, see Oppert (op. cit., pp. 338-58), who opines that, long before it was identified with Vishnu, it had been an object of worship with the aborigines and regarded as an emblem of female energy.] they are the embodiment of Vishnu; in the shape of the linga and yoni of Siva and Mahadevi or of the creative principles of life.[footnote: In the domestic chapels of orthodox Hindus, especially among the Marathas and the Smarta Brähmans of the South, five consecrated stones are commonly found, viz. the vana-linga of Siva, the Salagrama of Vishnu, a metallic stone symbolizing the female principle (Sakti) or Parvati, a crystal representing the Sun, and a red stone representing Ganesh. C.f Monier Wiliams, op. cit., p. 69 and 392; Thurston, Castes and Tribes of Southern India, vol ,i .p 315; and ERE. xi, 872.]

"Frequently they are in their natural State (Sayambhu, untouched by hand[footnote: Cf. Crooke, op. cit., p. 319.]; at other times they are crudely shaped, and at others finely chiselled and highly conventionalized; but whether worked or unworked, they are reverenced either for some inherent virtue of their own or because they are permeated with the spirit of a deity.[footnote: The idea of stone being animate or permeated with a soul presents on difficulty ot the Hindu mind, which believes that metempsychosis does not stop at animal existence, but that any natural object may have a soul and may become the abode of even the divine soul. Cf. Monier Williams, op. cit., p. 339.]

"Now, at Mohenjo-daro and Harappa there are three classes of aniconic objects generally of stone but occasionally of other materials also, that claim attention. The first class comprises those of the type illustrated in Plates XIII, 3, and XIV, 2, 4, and 5 . Two of these (Pl. A1, 2 and 4) are unquestionably phalli, more or less realistically modelled, and prove conclusively that phallism in India had a pre-Aryan origin, thus disposing once and for all of the fantastic theory that it was introduced into India by the Greeks or other Western invaders. Further evidence on the same point is furnished by two realistic specimens of the same kind—one a linga or phallus (PI. XIII, 1) and the other a yoni or vulva (Pl. XIII, 7), which Sir Aurel Stein found on chalcolithic sites in Northern Baluchistan, the former at Mughal Ghundai, the latter at Periano Ghundai. The other objects in this class (Pls. XIII, 3, and XIV, 5) [footnote: Cf. also Pl. CLV, 16-23 and 25.] are more conventionalized in shape, and their character, therefore, is not so obvious. They vary in size from half an inch to a foot or thereabouts in height, and are made generally of limestone or alabaster, but the miniature ones are also made of shel, faience, and paste, the last mentioned being sometimes coloured to simulate carnelian. These miniature specimens might have served as gamesmen, but the larger specimens are much too heavy for that purpose, and their shape does not suit them for use as weights; nor si there any other utilitarian purpose that can be suggested for them. Indeed, the only explanation applicable to them all is that they were sacred objects of some sort, the larger ones serving as aniconic agalmata for cult purposes, the smaller as amulets to be carried on the person, just as miniature lingas are commonly carried by Saivites to-day. And that these objects were, in fact, lingas sems highly probable from their shape, which in spite of its conventionality, inevitably cals to mind the linga from Mughal Ghundai (PI. XIII, 1). In mediaeval and modern India it is only very rarely that lingas take at all a naturalistic form. Ninety-nine per cent of them are so conventionalized that most people would find a difficulty in recognizing their phallic character (cf. Pl. XIII, 8). [footnote: This and Fig. 13 on the same Plate are modern miniature lingas and yonis carried as amulets.]

"As a fact, the resemblance between the stone objects under discussion and the Mughal Ghundai linga is closer than at first sight appears. Some of the former (Pl. XIII, 2) differ from their fellows in that they consist of the upper part only and are provided with small holes (visible in the photographs), as fi they had been attached to a base of some sort. [footnote: Mackay suggests that these particular stone pieces may have ben capitals of columns superimposed on wooden shafts, but this suggestion fails ot take account of the curved and finely dressed protuberance on the top, which would be incomprehensible if an architrave was intended to be bedded on it.] Now, the same characteristic is observable in the linga from Mughal Ghundai, but in this case the material of which it is composed is terra-cotta instead of stone, and the base or whatever it was to which it was attached was made in one piece with it, and has been broken of at the juncture. On the analogy of the Siva linga this base may be assumed to have been a yoni; and it is a reasonable inference that yoni bases were also affixed to the stone pieces exemplified in Pls. XIII, 2, and CXXX, 12 and 23, the bases perhaps taking the form of the ring stones described below.

"An instructive parallel to these phallic-like objects is afforded b y the so-called " chessmen" pillars of Dimapür and Kasomäri Pathar in Assam, which are believed to be memorial stones erected in memory of local heroes and which the late Dr. Bloch ascribed ot a non-Aryan people. That these chessmen columns were originally phallic monuments si suggested by the fact that in the non-Aryan districts of the south the custom still obtains, ro did so until recently, of erecting lingas on the graves of local heroes. It should be added, however, that along with the chessmen pillars in Assam, other pillars of a different type are found, some V-shaped, some like buffalo horns. [footnote: Cf. T. Bloch, "Conservation in Assam," ASR. 1906-7, PP. 22-3 and fig. 3. Dr. A. B. Cook tells me that "grabphalli" in the shape of chessmen or balls on pillars are found ni Phrygia used as gravestones on tumuli (A. Koerte in Ath. Mith. 1899, xxiv, 6 f., and pl. i, 1), and that they occur also ni Etruscan art either as grave stelai or a boundary stones.]

"The stones of the second class (Pls. XIII, 4-6, and XIV, 3 and 7) are even more varied in size than those of the first, some of the larger specimens being as much as 2 to 3 feet in height. In shape they are like many of the lingas seen ni Siva temples to-day, and have been taken to be such by most of the Hindus who have seen them. We must not, however, alow this resemblance to mislead us. They may be phallic in character. There is nothing ot prove that they are not. But prima facie it is unlikely that the phallic emblem would have been conventionalized in two different forms in the Indus Valley, and if a choice has to be made between the first and second classes of these objects, the shape of the former clearly gives them more title to be regarded as phallic than the latter. Moreover, though they resemble the Indian lingas, they equally resemble the batylic stones of Western Asia, such as the Semetic massebah, to which there is no reason to attach any phallic meaning,[footnote: A good example of such baetylic stones has recently ben unearthed in the temple of Mekal at Beisan (Daily Telegraph, 13th April, 1929); another was the world famous omphalos at Delphi.] and it would be in no way surprising if these baetylic cults of the Near and Middle East, as well as those of the Mother Goddesses discussed above which appertained to this same cultural area, proved ot have a closer connection than that arising out of a mere community of social customs. We need not, however, go so far afield as Western Asia to find parallels for this baetylic worship, since in India itself baetylic stones, such as those which guard the fields and crossways, are just as numerous as phallic ones and are common objects of worship with the primitive tribes, among whom they are specially associated with the Mother Goddess.[footnote: It may be recalled that there is a representation of the Phrygian Mother Kybele, showing her in human form in al other respects but with a head fashioned like the round top of a baetylic pillar, and there can be little doubt that she was once worshipped in that aniconic form. Cf. Farnell, op. cit., p. 63-4.] The only reason, therefore, for interpreting the Mohenjo-daro examples as phallic rather than baetylic is that their conical shape is now commonly associated with that of the linga. In reality, however, this point is a negligible one ; for nothing is more likely than that, as Saivism developed, it largely absorbed the older baetylic worship and appropriated its symbols to phallic worship. This would explain why the vast majority of mediaeval and modern lingas are fashioned more like baetylic cones than phalli.

"The interpretation of these two classes of stones suggested above does not preclude the smaller examples, which are made of faience, bone, shell, and ivory, as well as of stone, having served as gamesmen. The use of phalli as protective and apotropaic amulets or as luck-bringing talismans is world-wide, and as common in India [footnote: Miniature lingas made of stone, glas, and other materials are frequently caried by Saivites, and invariably by members of the Saiva sect of Lingayats, who wear them in a little casket suspended round the neck. In Babylonia the phallus was employed as an amulet from the second millennium onwards. One of the royal chronicles of about 1100 BC.. is inscribed on a tablet in the form of a phallus. Farnell, op. cit., PP. 229-30.] as it was, for example, in the Roman world, or as it still is, for the matter of that, in Italy. Whether in the days of Mohenjo-daro they were also endowed with apotropac or lucky virtues, we are unaware, but, assuming that something of the same idea attached to them then as in historic times, nothing would be more natural than that the pieces used in games of chance or skill should be fashioned after the same model and thus bring luck ot the players. And the same argument would, of course, apply equally to the miniature models of baetylic cones. This, however, is a surmise based on mere assumption, since at present we have no proof that any of these objects were used for games, though their resemblance ot Egyptian gamesmen undoubtedly warrants that inference.

"The third class of these stone objects comprises ring-stones of the types illustrated in Pls. XIII, 9-12, and XIV, 6 and 8. These ring-stones are found in large numbers at both Mohenjo-daro and Harappa. In size they range from half an inch to nearly four feet in diameter. All the larger specimens are of stone; the smaller ones of the same material or of faience, shell, or imitation carnelian. The most typical of them have their upper and lower surfaces undulating (Pls. XIII, 9 and 10, and XIV, 6 and 8 ); in others, the lower surface is flat, and the top takes a quatrefoil form (Pl. XIII, I and I2). An explanation of these ring-stones that has been suggested to me by Mr. Henry Cousens is that they were threaded on poles to form columns, but this suggestion leaves out of account the smaller specimens, some of which are no bigger than finger rings and obviously could not have served as architectural members.

"Another suggestion, but an equally unlikely one, is that they were Stone money I similar to the stone wheel-money in use on the islands of Uap in the Carolines. This stone money consists of large solid wheels or discs of limestones or aragonite 'quarried and shaped in Babelthuap, one of the Pelew islands, 400 miles to the southward. They vary in diameter from one foot to twelve feet, and each of them has in the centre a hole for the insertion of a pole sufficiently large and strong to bear the weight and facilitate transportation. They are known as fei. The limestone of which they are composed, to be of the highest value, must be fine, white, and of close grain. They are cut as nearly circular as primitive resources permit. The hole in the centre is roughly about one-sixth of the total diameter. From their size and weight they are frequently not capable of being stored in the native houses; and since they are not easily stolen, they are (perhaps more often than not) kept outside. Thus, as one traveller says, "they are more for show and ornament than for use." The houses of the richer men, and the failu or pabai, the men's house where the men live and hold their councils and assemblies in every village, have their fronts adorned with fei that testify to the wealth of the inmates. The value depends not only on size, but also on the quality of the material.' [footnote: Cf ERE. vol. i, .p 869; W. H. Furness, The Island of Stone Money, 1910, p. 93; F. W. Christian, The Caroline Islands, 1899, pp. 236, 256 291. Since the above was written Dr. A. B. Cook has drawn my attention to the fact that relatively small discs of quartz and sandstone pierced with a hole in the centre were once used for money in Togoland.]

"This wheel-money of Uap undoubtedly presents a Striking parallel to the larger class of ring-stones of the Indus Valley, and for this reason I have quoted the above extract at length. Like the previous one, however, this explanation does not take account of the smaller ring-stones, many of which are obvious replicas of the larger ones and may be presumed, therefore, to be of the same character. And there are other inherent objections also. In the Indus Valley Stone was doubtless a rare commodity, but ni the Chalcolithic Age it could not have been of such rarity as to warrant its being converted into money, nor is it credible that people who had reached the advanced stage of cultural development evidenced at Mohenjo-daro and who were in close commercial and other relations with countries as far distant as Persia and Mesopotamia, would have resorted, even for local purposes, to so cumbrous a medium of exchange. It is conceivable, no doubt, that at a much earlier and more primitive stage stone might have done duty as money; and we may believe, too, that this money would come to be regarded as a sign of wealth and power, as it is in the island of Uap, and been retained as such until a relatively late date. In such matters India has always been peculiarly conservative, and the possibility of this having happened cannot be entirely set aside. All things considered, however, a more reasonable and adequate explanation of these ring-stones is to be found in the magical properties which holed and ring-stones have from time immemorial been supposed to possess and in the universal awe in which they are held in India, whether as fetishes or as actually imbued with a divine spirit. A well-known example of this class of stones is the Srigundi stone at Malabar Point, near Bombay, which is supposed to purify those who crawl through it of sin or sickness. It was through this stone that that Sivaji crawled to purge himself of the murder of Afzal Khan, and others of the Maratha Peshwas followed his example.[footnote: Cf. Crooke, op. cit., p. 322. Gazeteer of Bombay City, 1909-10, ii. 360.] Another famous one is at Satrunjaya, the hole in it being known as muktdwara (door of absolution), through which anyone can creep is assured of happiness. [footnote: ERE. i, 874, and A. K. Forbes, Ras Mala, p. 574. For other examples the reader may consult Crooke, op. cit., and ERE. ii, p. 874.]

"These and same stones of the same class are definitely regarded as yonis or female symbols of generation [footnote: Cf. Crooke, op. cit., p. 322.], the idea being that those who pass through them are, as it were, born again, while in the case of the smaller stones of the same form the mere passing of the hand of finger through them is an act of special stones at virtue or significance. That the same idea attached to ring-stones as far back as the Mauryan la period is evident from several examples of them of that date which I recently unearthed at Taxila (Pls. XIII, 14 and CLIX, 9and 10). In these ring-stones, which are quite small and used perhaps as ex-voto offerings, nude figures of a goddess of fertility are significantly engraved –with consummate skill and care–inside the central hole, thus indicating in a manner that can hardly be mistaken the connection between them and the female principle. These rings, it is true, carry us back no further than the third century B.C., between which and the Chalcolithic Age there is a very wide margin of time. Indeed, were there no direct evidence of yoni and linga worship having been practised in that age, I should hardly venture to use them as an argument. That, however, is not the case. We have already seen that the presence of phallism at Mohenjo-daro is proved by the discovery of realistic lingas, as to the character of which there is no question; and that in the neighbouring country of Baluchistan the worship of the yoni is similarly attested at Periano-ghundai. We are justified, therefore, in supposing that the ring-Stones found at Mohenjo-daro may have had the same cultural, fetish or magical significance that the ring-stones of a later date had. We cannot yet prove that they possessed it, but the hypothesis is reasonable, and it is the only one yet advanced that adequately explains these curious objects. We must not, of course, infer that each and every holed stone found on this site was of the same character. That would obviously be absurd. We are concerned only with those ring-stones for which no utilitarian purpose can be suggested and for which no other adequate explanation is forthcoming.

"To conclude these observations on stone worship, I distinguish three types of cult – stones at Mohenjo-daro and Harappā—the baetylic, the phallic and the yoni ring-stones. Each of these types is represented by numerous examples, both small and large, the former much predominating over the latter. The larger specimens I take to be objects of cult worship; the smaller ones to be amulets for carrying on the person, just as miniature lingas and yonis are still commonly carried (cf. Pl. XIII , 8 and 13), but it is not unlikely that some of the smaller specimens may also have served as gamesmen. Whether these three types represent three distinct cults is uncertain; but it is not unnatural to suppose that linga and yoni worship may have been associated then, as they were later under the aegis of Saivism. On the other hand, it is probable that they were originally quite distinct from baetylic worship, which is found frequently connected with the cult of the Mother Goddess among the oldest tribes, whereas phallism is rarely, if ever, found among these aboriginal people."