CONCHOLOGY. 



21 



>!) a living ftate. For no{ only /ingle fpecies of foiTil 

 il.clls yet remain undifcovered in their living Itate ; but 

 gcntra, and even whole tainilies, (till exill in the Teas, 

 which are not yet known to ns, othervwle than in the (oikl 

 ftp.te. Foffil limpets are very rarely met with ; however, 

 there are two kinds, which delerve particular notice. 

 The iirll is a fmall I'pecies called the fool's cap. It (eenis 

 different from the Weft Indian kind, but approaches it 

 nearly. This is not unfrequently found in the calca- 

 jenus foils of France. The lecond is a very curious and 

 remarkable Ihell, and the fragments of it, called by foflilo- 

 gifts tiichites, are found in great abundance in the Eng- 

 iiih chalk-pits ; ytt the Ihells are fo rarely to be met with 

 entire, that we have heard of only four, which were found 

 ill the cliffs near Dcfver. Thele limpets are very large, 

 :uk1 nearly refemble a fmgle fliell of- a bivalve. They 

 feem to be of two kinds, and are more irregular than that 

 fiiell ; and, inftead of being fulcated lengthwife, they are 

 circularly wrought, or in a tranfverfe manner, with very 

 high irregular ridges, n t thickly, but rather thinly, (et. 

 Thefe flieils are very thick. One fort is high, or coped, 

 the other is broad or flattiHi. The infideis quite fmooth, 

 the edges turn outwards, and, under the beak, or that 

 part which anfWers to the hinge in bivalves, they ftretch 

 out, towards the fame fide, into a broad flat ledge, the 

 perpendicular lide of which is curiouOy worked with 

 itraight and parallel furrows, like the hinge of a multar- 

 ticulate bivalve. On the top or beak it has a large, wide, 

 roundifh opening, which, from its remarkable thinncfs, 

 makes it difhcult to determine whether it be a natural 

 jierforation, or an accidental fraiSIure j though, by its re- 

 gular edge, and being quite alike in all the four fpecimens, 

 one would incline in favour of the former. Figures of 

 tlie limpet are exhibited in the engraving. 



HALIOTIS, AURES MARIN^'E, or SEA EARS. 



The effential charafler of this family is as follows: 

 fhells of an ear-like form, flattifh, almoft wide open, or 

 iioUow, for, from the apex or head, all along one fide, it 

 lias only a broad ledge or margin. The apex has alfo a 

 fingle perfeft whirl ; and a curved row of holes, or per- 

 forations, runs its length, from the head to the oppofite 

 =cnd. Thefe Ihells, in appearance and nature, approach 

 very nearly to the limpets, and, in like manner, afK.K 

 themlelves to rocks. However, they cannot truly be 

 called limple, or Iliells that are no way fpiralj becaufe at 

 their head they have as perfeft and fine a whirl as any tur- 

 binated fliell : but, as nature in her works has made fuch 

 flight tranfilions from one link to another, it is almoft 

 impoflible to fix them by human definitions. Thus, fe- 

 veral of the chambered limpets have only fuch fingle 

 whirls; and the trocho patella, and cochlea patella, are 

 often fo greatly fpiral, as exteriorily to refemble a trochus 

 or a (hail ; yet they are true limpets. It is therefore im- 

 puliible to regulate natural objefts to a perfeftprecifion, by 

 the moft elaborate and minute definitions. 



The fpiral iiead of the haliotis has induced many au- 

 thors not only to feparate them from the limpets, but 

 alfo to rejeft them from the fimple Iliells. Thus Lifl:er 

 places them in his Hiftoria Cmichyliorum among the tur- 

 binated Ihells, after the nautiii, the fnails, and the uerits, 

 and preceding the trochi. He does the fame in his work 

 de Animalibus Anglis, wherein he fays, it is fpiral at the 

 •clavicle in the fame manner as other turbinated fliells, and 

 therefore by fome is wrongly placed among the fimple 

 Ihells. Gualtieri ranks them among the fnails with de- 

 prefi'ed or flatted clavicles; and Adanfon arid Meufchen 

 take them from the fimple fliells, and place thcra as the 

 firlt family of the fpiral fliells: Dr. Graclin has placed 

 them the iaft of the fpiral fliells. Linnaeus allows no fliell 

 to he of the haliotis family, without having the row of 

 perforations; which is an eflential charafter. Thus the 

 Venus ear, ranked by Ibme as a haliotis. Da Colta and 

 LinniEusfeparate from them. But there isalfo another ch.i- 

 raiter, which feems to belong to this family ; that is, 



Vol. V. No. 150. 



their infide is alw.iy3 of the fineft or moft orient pearl; 

 and even pearls are often bred in them. This is another 

 reafon why the Venus ear belongs not to this family, for it 

 vijnts the pearly infide, as weTl as the perforations. In 

 the row of holes which confl:itute thefe perforationr, 

 there are generally fix or feven quite perforated, or very 

 open ; the reft are clofed, and appear rather like tubercles 

 than holes ; for it is laid the fifli alw-ays clofes one towards 

 the end, as he increales in fize; and by thele holes he 

 calls forth his excrements. 



There are but few fpecies of this family. It is even 

 doubted, whether fonie of thole propofed by dilferent 

 authors, are not rather varieties: but they are found ia 

 great abundance in moilpaits of the world, in their ufual 

 and cuflromary kind. Dr. Ginelin enumerates nineteen 

 fpecies. There is no inllance on record of a haliotis 

 being found foffil. A figure of the haliotis is given ia 

 the engraving. 



OF CONCAMERATED VNll'ALrES. 



The fccond divifion of univalves, contains the conca- 

 merated or chambered fliells, that have many regular and 

 nearly equidillant cells or chambers, and a pipe or fi- 

 phunculus, that opens into, and comm.niicatcs from, 

 chamber to chamber. This liruflure forms the elTcntial 

 and fpecific charaftcr of the fliells of this divifion ; for 

 there occur among them not only revolved and turbi- 

 nated fliells, but even quite fimple, or no-wife turbinated 

 ones. The Ihells of this conformation conltitute the fifth 

 family of univalves, and is divided by Da Cofta into fix 

 genera, one genus whereof, viz. the orthoceratites, is of 

 a fimple figure ; four genera, as the lituits, or croziers, 

 polythalami, turbines ammonia and amir.onoides, araall 

 turbinated; and the other genus, or nautilus, is revolved. 



For the arrangement of thefe chambered Ihells, we are 

 obliged to have recourfe to the foffil kingdom; Cnce 

 there are only two genera out of the fix, viz. the lituitrs 

 and the nautilus, that aie known recent from the fej. 



Yet it is furprizing, that thefe genera, which are found 

 foflil in fuch amazing abundance all over the globe, and 

 form numerous families, have to this hour efcaped the en- 

 deavours of mankind to obtain them living. Befides 

 other reafons that have been given, their being pelagian 

 Ihells, or fliells that inhabit the very deepelt recefles of 

 the fea, feems one principal caufe; as thofe fituations arc 

 not fubjeft to the agitations of the great tempefts, and 

 other violent ragings of that immenfe mafs of waters; 

 and therefore thele Ihells feem conftantly to remain uh- 

 dillurbed in thofe imraenfe deeps. 



The ORTHOCEROS. 



Thefe are fimple ftraight conical fliells, no-wife turbi- 

 nated ; and gradually tapering from a broad end to a. 

 Iliarp-pointed top, like a ftraight horn, whence their name. 

 They ai-e chambered fr^om bottom to top, and have a fi- 

 phunculus, or pipe of communication, from chamber to 

 chamber. Planchus, in his book de Conchis minus no- 

 tis littoris Ariminenfis, defcribes fome recent minute 

 kinds of this genus, which he found in great quantities 

 in the fea lediment, at Rimini, in Italy. The orthoceroles 

 he difcovered were fpecies fo very minute, lefs than one 

 quarter of an inch, and not thicker than a pin, that they 

 demanded the aid of the microfcope to afccrtain their 

 ftrufture. Linnaeus, in his order of fliell-fifli, ranks them 

 as the nautilus orthocera. 



How difterent thefe living fpecies are from thofe found 

 foflil, is extremely ftriking ; the recent fpecies are fo ve- 

 ry minute, as to demand the microkope to examine them ; 

 the foflil ones, on the contrary, are moftly very large, 

 frequently above a foot in length, and above an inch and 

 a half over; even the fmalleft kinds, as the alveoli, are 

 feldom lei's than an inch long, and a quarter of an inch 

 over : and befides their great difference in, fize, they no 

 wife correfpond in other particulars with the larger, fo as 

 to be imagined young ones of the lame fpecies. Brey- 

 G nius. 



