CONCHOLOGY. 



i; 



numVr of little prifms, placed in all kinds of dire6lions, the rudiments of a proper apparatus for making t!ie epi 



which refrart tb'e rays of light, and produce all the 

 changes of colonr obfetvable in thefe (liells. 



VVrth refpeft to the figures and colouis of (hells, it is 

 ■obferved, that river (hells have not fo agreeable or diver- 

 fified a colour as the land and lea fhelis ; but rhe vai ieiy 

 in the figures, colours, and other characters, of ie.i flseils, 

 is almolf infinite. The number of diltinft Ipecies we find 

 in the cabinets of the curious is very great; and doubt- 

 lefs the deep bottoms of the lea, and the iliores yet un- 



dermis, as well as the fiiell. ' The itruif ure of the epider- 

 mis is very different in different genera. In feme it is 

 lanr.nated, in others fibrous and brufh-like. It delerves 

 to be more minutely examined, and it feenis not impro- 

 bable but among the iiveral ufes of this covering, the 

 two following may delerve confideration: i. To prevent 

 the fait water from corrodingthelhell; forall (liells thathave 

 an epidermis have a I'cabrous furface. 2. To prevent other 

 lliell-fifh or marine inleits from fixing their habitations 



explored, contain multitudes ftill unknown to us. Even on thefe (liells, as they do upon all bodies in the fea. 



the fame Ipecies differ in foiiie degree in almoft every in 

 dividual i (b that it is rare to find any two (liells which 

 are ftriflly alikfrin all refpefts. This wonderful variety, 

 however, is not all the produce of one fea, or of one 

 country; the different parts of the world afford us their 

 different beauties. Bonani obferves, that the moft beau- 



where there is not a power of defence. And this renders 

 it very probable, that all fiQies inhabiting naturally fraooth 

 (liells, are capable of not only adding to the extent and 

 growth of their (hells, but can likewile, from time to time, 

 add a frelli poliflied covering to the whole (hell ; at lead 

 their organs (eem to extend to fuch a length, as to clear 



tiful fliells we are acquainted with, come from the Eaft away all impurities from their (hells. We (eldora find any 

 Indies and from the Red. Sea. This is in fome degree cowries with coral, or extraneous bqdies adhering to any 

 countenanced by what is found to this day; and, from part of them. 



the general obleivations of the curious, it litems, that the 

 fun, by the great heat that it gives to the countries near 

 the line, exalts the colours of the (hells produced there, 

 as it does the rich plumage of birds, and the more ele- 

 gant decorations of ferpents ; and hence gives them a 

 luft'-e and brilliancy that thofe of colder climates always 

 ■want : and it may be, that the waters of thole valt feas, 

 which are not (ubjedf to be weakened by frc(h rivers, give 

 a nourifliment to the fifh, that may add to the brilliancy 

 of their (hells. 



Of the PARTS and CHARACTERS of SHELLS. 

 In every fylfem of conchology, it is neceflary to fix 



The head, (apex,) of an univalve, is the part julf over 

 the mouth or aperture. The bale, end, or tip, (bajln,feit 

 acumen,) is that part of the other end oppofite to it, or 

 the end of the turban; though fome authors have given 

 them quite contrary names, by calling the tip or turban 

 the part over the mouth. In (peaking of (hells it may be 

 underftood, that when the upper or under (ide, or ends, 

 are mentioned, it is fuppofed that the (hell lies on its 

 mouth upon a table, with the head towards the right 

 hand, and the end or tip towards the left. 



The body of the (liell, (corpus,) is that part which runs 

 from the top to the extreme limits of the aperture, and 

 occupies the fpace between tlie bafe or turban, a.-id the 



fome ftandiird or elTential cliaraflers to all (hells, by which apex. A whirl, turn, fpire, or wreath, (j'pha, anjyatlus,) 

 they may be divided into families or clalfes, genera and denotes each (ingle or (eparate turning or circumvolution; 



J'pecies. Thefe charafters mult always be formed from 

 the chief parts of the (hells, the differences of which, in 

 (hape, fize, fituation, or other marks or particularities, 

 enable us to form refpeftive families or clalfes, and to re- 

 Iblve thole families into genera, and afterwards into (pe- 

 des, by other fubordinate charaflers. Thus iu univalves 

 there are five llandard or clVciitlal churaA^rs for the clalfes 

 or families: thefe are, i. Simple or not turbinated. 2. 

 Turbinated, witlr a fingle continued cavity. 3. Turbi- 

 nated and chambered, or with many compartments or 

 cavities. 4. The peculiar (hape. 5. The aperture, mouth, 

 or opening of the (hell. The fubordinate cbarailers for 

 genera and fpecies in univalves, are, i. The number of 

 fpires, convolutions, rounds, or wreaths. 2. Whether 

 operculated, or covered with a lid, or not operculated. 

 3. The (lielly fubrtance, whether opake, horny, pearly, 

 &c. 4. The epidermis. 5. The head, beak, or tip. As 

 thefe charafters include the principal parts of all uni- 

 valves, they of courfe conftitute the rudiments of the fyf- 

 tem; which rud i ments ought to be well inveftigated by every 

 col leif or of (hells. It is laudable to coUeft ; but when a 

 colleflor alfo makes it his (tiidy to contemplate fcientifi- 

 cally the natural curiofities he acquires, he then claims 

 the'ielpefl of mankind, in addition to the praife already 

 gained by his aHiduity. 



The particular parts which enter into the conftruflion 

 of a (hell, are as follow : i. The epidermis, or periolfeum. 

 This part is common to bivalves as well as univalves. It 

 is a rough covering or (kin, which raolf, but not all, (hells 

 have ; and only on the outfide, never withinfide, the (hell. 

 The epidermis, perhaps, is a periofte or membrane, that 

 c6vers the (liells to defend them from exterior accidents, 

 to prelerve them, and aid their growth. In that it does 

 the f'sme office as the periolte or membrane which covers 



as in the turban of the whelk, or common (hail. The 

 difpofition of the fpires, fays Mr. Adanlbn, is not the 

 fame in all (hells; it varies according to the diflerent 

 plans they turn on, and they can turn on four different 

 plans, which are; i, the horizontal; a, the cylindric, 

 or (preading on a cylinder; 3, the conic; and, 4, the 

 ovoid plan. From thefe four difpofitions of the (pires, 

 all tiie different forms or figures of (liells pioceed. The(e 

 are the principal difpofitions of the fpires ; but there are 

 many intermediate ones, which proceed from different 

 degrees and combinations of thefe four. The number 

 and forms of the fpires vary in the fame fpecies, either in 

 their different growths or. fexes. Young (liells have al- 

 ways a lefs number than the old ones ; the realbn is, be- 

 caufe all turbinated or fpiral (hells take their growth from 

 the tip or end, to the mouth or upwards. Some diells 

 though of the fame age, foinetimes have not the fame 

 number of fpires: this is to be .attributed to difeafe; or 

 perhaps, it may be an effeft of fex. Thus, in the pur- 

 purs, the buccma, and in fome other kinds, it is com- 

 mon for the males to have their fpires lefs numerous 

 more ilender and lengthened, or lefs fwelled; and the 

 whole (hell fraaller than in the females. This obfervation 

 is always found to be conllant. 



The turban, or clavicle, ( clci'-viaila,) is the asjgreeate 

 or whole fet of the whirls, and always forms the 2o%i.er 

 part ot the fliell. A flat tut bail, or helix, (cla-juula helix.) 

 IS fo (lightly prominent, as to be nearly on a level with 

 the bale of the (hell. There are likewii'e (i;veral ether 

 degrees of them, as the Qiort turban, (claiiicula dcprelfa ■) 

 the produced turban, (clamicula lengiorc;) the ion" tur- 

 ban, (cUfuicula longiffma ;) all which are explained br 

 the very names they bear. 



The pillar, (columella,) is the middle part, or axis 



^ 1- I 1 11 C f 1\ t"/-lll .-vll f'i-l.J 'lli.Il ^m- X*.. ». _ . . . 1_ . _ 



the bones of other animals ; for the (liells of thefe filhes which runs through the ihell, or from top to bottom, and 



m.iy be confidered, and indeed are, quite analogous to 

 the bones of other animals. The epidermis feems as much 

 a genuine covering of the (lic;ll formed by the fifh, as the 

 ftiell itfelf. And, could we (ise the recent fifli, and ex- 

 amine its organs, there is no doubt but wfrlhouldlind 

 Vol. V. .No. 250, 



from which all the fpires commence and turn round, and 

 which forms the fupport or balis of them. It always lies 

 afide the mouth, and though not feen in all the (lulls, yet 

 in many it is the raoft obvious part of the mouth next the 

 lip. The mouth or aperture, (apertura,) needs no ex- 

 f plauatioii. 



