49 



LITHOPHAGID^C. 



LITHOPHAGIDJE. 



170 



marked, nearly contiguous ; hinge composed of slender, approximated, 

 and nearly parallel teeth, two in the right valve, and three in the left, 

 or three in each ; posterior ligament a little elongated, and in great part 

 external ; muscular impressions oval, the posterior one the most rounded, 

 both united by a pallial impression deeply excavated posteriorly. 



Such is the character given by M. Rang, who apparently restricts 

 the generic name to those species which excavate stones, &c. " The 

 shells," says M. Rang, " which compose this genus are lithophagous, 

 and excavate in stones and madrepores cavities more or less propor- 

 tioned to their form and to their volume, wherein they lodge them- 

 selves, and out of which when adult they cannot go, the aperture of 

 the excavation being too small to admit of their egress. They are 

 without an epidermis, and generally of a dirty white." 



M. De Blainville, who knew not the animal when he published his 

 ' Malacologie,' divides the genus into three sections : the first exem- 

 plified by Venerupit Irus ; the second by V. Rupellaria (Rupellaria, 

 Fl. de Bell.) ; third, by V. lamellosa (Petricola, Lam.) ; and he remarks 

 that if the system of ' engrenage' of the species of excavating Veneres 

 be regarded rigorously, we should be compelled to establish as many 

 genera as there are species. He adds that he has chosen Venerupii 

 from among the denominations proposed for some of these genera, 

 because it well indicates that the species composing it are Veneres of 

 the rock. 



Mr. G. B. Sowerby (' Genera," No. xxviii.) notices the difficulty of 

 ascertaining any distinguishing character between the Lamarckiau 

 Venerupis &aH VenusPullastra&ud V. detussata, and others, except in the 

 apparent habits ot the animals ; a difficulty which had prevented him 

 from endeavouring previously to clear up a point to which his attention 

 had been frequently directed, but which he thinks he has at last 

 overcome. " It is well known," continues Mr. Sowerby, "that Venus 

 perforans, Mont., Venerupii perforans, Lam., and some of its congeners, 

 live in cavities perforated in chalk and limestone rocks, and that the 

 Venus Pullastra, V. decussata, and several other species that resemble 

 them in general form and appearance, are found buried in the sand ; 

 an apparently well marked difference therefore exists in the habits of 

 their respective animals. We think however that we have evidence to 

 prove that there exists in reality very little difference, and that the 

 cavities hi which Lamarck's Venerupea live are rather the natural con- 

 sequence of the action of the sea-water in conjunction with some of 

 the excretions of the animal upon the chalk or limestone, than of any 

 power of the animals themselves to pierce independently of such 

 action ; so that the difference is really only in the nature of the shore 

 on which the very young shells are accidentally deposited, those 

 which are thrown upon a sandy bottom burying themselves in the 

 sand, and such as are deposited upon limestone or chalk producing a 

 cavity in which they live." Mr. Sowerby then proposes to unite 

 together under one appellation Lamarck's Venerupes, and the following 

 of his Venerei : V. Malobarica, V. papilionacca, V. adspena, V. 

 punctifera, V, turgida, V. litterata, V. rulcaria, V. textile, V. tezturata, 

 V. geoyraphica, V. rarijlamma, V. decussata, V. Pullastra, V. aurea, 

 V. mrginea, and some others : and for the genus thus constituted he 

 proposes the name of Pullattra, rejecting the term Venerupis, or 

 Vcnerirupit, because it would convey the false idea that at least 

 the greater number of tho species were inhabitants of rocks. 



M. De Blainville and M. Rang, as we have above seen, restrict the 

 genus Venerupis to the species that excavate rocks. 



Lamarck makes his Lithophages consist of the genera Sa.ticava, 

 Venerupis, and Petricola ; and quotes the opinion of M. Fleuriau de 

 Bellevue that boring shells generally do not pierce stones by the attri- 

 tion of the shell against the stone, but by means of a softening or 

 dissolving liquor which the animal sheds a little at a time. 



Lamarck observes that it is not his intention to assemble under this 

 family of Lithophages all the boring bivalves, or all that pierce stones ; 

 for, as he truly says, such an assemblage would be rather extravagant. 

 He refers to shells equally excavating with his Lithophages, which 

 cannot be separated, some from the Veneres, others from the Modiolce, 

 others from the Lutraria, others again from the Carditce, and remarks 

 that it is not of these that he is then treating. His Lithophages con- 

 sist of those shells, among the boring or excavating conchifers, that 

 gape more or less anteriorly, and have the posterior side short, 

 rounded, or obtuse, with the ligament of the valves always external, 

 which live habitually in stones, and for the reception of which he then 

 knew no particular family, or any family to which they might con- 

 veniently be approximated. He observes that he nevertheless places 

 among them some species the habits of which were not known to 

 him. To this M. Deshayes adds in the last edition (1835) a note 

 stating that upon the same ground that it would not be rational to 

 establish a genus or family for the JUodiolte, or the Carditce, which 

 pierce stones, it would not be right to reject from the family of the 

 Lithophages shells which do not perforate, but wherein we neverthe- 

 less find all the essential characters of the species which it contains. 

 For this reason it would be convenient to approximate the Byssomycs 

 and the HiateUa to the Saxicava, and to leave in this genus species 

 which do not perforate. M. Deshayes (loc. cit.), who does not appear 

 to have seen the observations of Mr. Garner and Professor Owen above 

 alluded to, refers to the discussions relative to the means by which 

 perforation is brought about by certain acephalous molluscs. Some 



uthors, he remarks, have supposed that the attrition of the valves 

 against the stone sufficed to wear it away by degrees, and that thus the 

 animal formed a lodgement sufficient to contain it. Olivi, he observes, 

 who was of this opinion, grounded it on the fact that he pretends to 

 have observed that perforating molluscs can attack lavas or other 

 rocks which are not calcareous. " Since this assertion of the Italian 

 author," continues M. Deshayes, " no well made observation has 

 occurred to support it, whilst, on the contrary, a great number of 

 proofs have been collected showing that perforating molluscs are 

 never lodged except in calcareous stones. This mode of life render.-* 

 very probable the opinion of M. Fleuriau de Bellevue, who believed 

 that the animal was provided with an acid secretion, by means of 

 which it dissolved, in proportion to its growth, the walls of the cavity 

 which it inhabits. An observation of my own is that the greatest 

 number of perforating molluscs are contained in close-fitting cavities 

 by no means made to permit of rotatory motion ; that they are oval 

 when the shell is of that form ; and that we almost always see rising 

 between the umbones of the valves a calcareous crest which forbids 

 any movement of rotation." M. Deshayes then proceeds thus : 

 " Many zoologists have believed that there was but little necessity for 

 preserving the family of the Lithophages. M. De Fe'russac places the 

 Saxicava! in the neighbourhood of the Gastrochcente and the Solens, 

 and he places the Venerupes near the Venerei. M. De Blainville has 

 adopted a nearly similar opinion. We do not admit it any more than 

 that of M. De Fe'russac, and we shall preserve the family of the Litho- 

 phages as Lamarck established it in this work. We rest our opinion 

 on the knowledge of many animals belonging to the three genera 

 Saxicava, Petricola and Venerupii; they are bound by a common 

 relationship (par des rapports communes) ; thus the mantle, which 

 scarcely opens for the pasaage of the rudimentary foot in certain 

 Saxicaoce, opens a little more in the Petricolce, and more still in the 

 Venerupes. The foot follows a nearly analogous development, always 

 remaining however proportionally smaller than in other molluscs in 

 which this organ is necessary for locomotion." 



Lamarck says of the Venerupes, or Venuses of the Kock, that they 

 seem in fact to have a hinge analogous to that of the Venerei, but 

 that nevertheless a slight difference in the disposition of their cardinal 

 teeth suffices to enable us to recognise the genus. They are, he adJs, 

 lithophagous or perforating shells which are very inequilateral, and 

 which are not distinguished from Petricola, except in having three 

 cardinal teeth at least in one valve. 



" The greater part of the Venerupes," observes M. Deshayes in his 

 commentary on this genus, " differ scarcely from the Petricolce ; they 

 offer most frequently three cardinal teeth in one valve, two and rarely 

 three in the other. When in some individuals one of these teeth is 

 abortive, which often happens, the same species may be comprised in 

 the two genera at once. The animals of the perforating Venerupet 

 are scarcely to be distinguished from those of the Petricola!; only 

 the mantle is a little more slit and the foot a little longer. In the 

 Venerei these parts are different ; and this proves that it is necessary 

 to keep separated two genera which Cuvier and M. De Blainville have 

 thought it right to unite or approximate. We do not pretend to 

 dispute, nevertheless, the analogy which is evidently exhibited between 

 certain Venerupes and the Veneres. We think that the Venerupes ouly 

 ought to be withdrawn from the genus and placed among the Veneres, 

 because the animals are iu fact similar ; only some plunge themselves 

 into hardened mud, whilst others live in the sand. An.}, although 

 they may enjoy the faculty of perforating stone, this would not be 

 a sufficient reason to reject them from the Veneres, because we have 

 seen that in a great number of genera belonging to very distant 

 familie' there exist perforating species ; thus we may well conceive 

 that there may be perforating Venerea, but that does not hinder us 

 from admitting a genus Venerupis, the characters of which appear 

 sufficient to us." 



The number of recent species of Venerupis is 19, and their range is 

 wide. Species are found on the coasts of England and France, in the 

 Mediterranean, in the South Seas, and in those of India, China, and 

 Australia. 



V. perforans is the Tapes Pullastra of Wood, the Venus perforans 

 of other authors. Shell sub-rhomboidal, concentrically striated, 

 running into strong wrinkles or ridges at the anterior side ; some- 

 times, though very rarely, with very fine longitudinal stria! ; 

 colour light-brown ; umbo very near to one end, small, and turned a 

 little sideways; the longer side much truncated; hinge with three 

 teeth in each valve, one of which is small, tho others long, slender, 

 and curving outwards; middle tooth a little bifid. Inside smooth, 

 white, with generally some purple at the truncated end ; margin plain ; 

 valves moderately concave. Length rarely exceeding 3-8ths of an inch, 

 breadth more than 5-8ths. 



Montagu, whose description this is with very slight alteration, says, 

 that with respect to shape it is difficult to fix any as a permanent 

 character; it is however, he adds, most frequently sub-rhomboidal; 

 sometimes nearly as long as it is broad, generally straight on the front 

 margin, but in some instances deeply sinuous or indented. 



It is very common on the coasts of England. Lamarck records a. 

 variety smaller and narrower, with sub-striated lamellae, from the 

 coasts of France, on the authority of M. Fleuriau de Bellevue. 



V. Irus is a common species on the British coasts. 



