40 



CONCHOLOGY. 



tliiny different fvecies of the cornua amnionis. They lie 

 immeri'ed iu a bluidi foflil ftone, of a foft texture and 

 fatty appearance, in prodigious numbers, and of a great 

 variety of (izes, from the larger forts down to fuch as 

 coiiid not be feen without very accurate infpedtion. Such 

 as lie in the fofteft of thefe ftones are foft like their ma- 

 trix, and eafily crumble to pieces ; others are harder. In 

 a piece of this ftone, of the bignefs of a finger, it is com- 

 mon to find thirty or more of thefe follils ; and often they 

 are (("en only in form of white fpecks, fo minute that their 

 figure cannot be diftingui(hed till examined by the micro- 

 fcope. They all confift of feveral fpirals, which are dif- 

 ferent in number in the different fpecies, and their ftrise 

 alfo are extremely various ; fome very deep with high 

 ridges between them, others very flight ; fome ftraight, 

 others crooked; others undulated, and fome terminating 

 in dots, tubercles, or cavities, towards the back, and 

 others havijig tubercles in two or three places. They are 

 all compofed of a great number of chambers or cells, in 

 ,t!)e manner of the nautilus pompilius, each having a 

 communication with the others, by means of a pipe or 

 fiphunculus. A fsw of the Imall fpecies have been fiihed 

 up alive; but the large and beautifully maiked ones are 

 found only follil. They are compofed of various foflil 

 bodies, often of quarry ftone, fometimes of the matter of 

 the common pyrites, and of a great variety of other fub- 

 Itances ; and though they appear ufually mere ftones, yet 

 in fome the pearly part of the original Ihell is preferved 

 in all its beauty. Sometimes alfo, while the outer fub- 

 ftance is of the matter of the pyrites, or other coarfe, 

 itony, or mineral, matter, the inner cavity is filled with a 

 pure white fparofthe common plated texture. This gives 

 a great beauty to the (pecimens, many of which are dug 

 cur of the aluin rocks in Yorkdiire. 



M. de Lanunon, a French naturalift, who accompa- 

 nied La Peroule in his late voyages of difcovery, feems 

 tu agree with moft conchologifts, that the larger cornua 

 anunonis may rtill exift in the fea; but he thinks they are 

 in very fm.ili number, and materially different from the 

 greater part of the follil (lieils above defcribed. He con- 

 tends that thofe ought to be confidered as a race, for- 

 merly the moft numerous of all, of which, either there 

 are no defcdndants, or thofe defcendants are reduced to 

 a very few degenerate individuals. That there are no 

 living animals with fliells of the -very fame kind with fome 

 of the foflil cornua ammonis, the following obfervations 

 he confiders as a fufficient demonftration : — " The foflil 

 fiiells are very light and thin, whereas the ftiells of thofe 

 animals that live in very deep water aie always thick and 

 ponderous; b.liiles, the form of the foflil cornua ammo- 

 nis points out to us, in fome meafure, the organization 

 of the animal which inhabited it. The celebrated Juflieu 

 proved, in lyii, that there exifted a very clofe analogy 

 between the ammonite and nautilus. It is well known 

 that the nautilus, by filling or emptying a part of its fhell, 

 has the power of remaining ftationary in any depth it 

 pleafes : the fame was doubtlefs the cafe with the ammo- 

 nite ; and if this fpecies ftill abounds in the fea, it would 

 furely be occafionally discovered by failors. The waves 

 alio would throw fragments of it on the fliore ; fiftiermen 

 might fum-times entangle it in their nets; or, at leaft, 

 there would be fragments fticking to the lead ot the 

 founding-line when aicertaining great depths. It may 

 alfo be ailded, that if the ammonites never quitted the 

 ahyfs of the fea, tholi: which are found petrified would 

 iio't be conlbantly met with on the lame level, and in the 

 lame bed, as thofe ftiell-filh that only inhabit the ftiallows. 

 Yet there are found, in a multitude of places, ammonites 

 mixed with turbines, buccina, and other littoral (hells. 

 They are found, belides, at every degree of elevation 

 from below -the level of the fea to the fummits of the 

 higheft mountains. Analogy alfo leads us to fuppole, 

 tli.it nature, who has given eyes to the nautilus, has not 

 rel uled them to the ammonite : now what ule could thefe 

 be of if they remained confined to thofe depths which the 



light is unable to penetrate. The extinction of the an- 

 cient race of ammonites is therefore a faft, which no ra- 

 tional i'uppofition can deftroy ; and this fait is undoubt- 

 edly the moft furpriiing of 'any that is prefented to us in 

 the hiftory of aquatic animals. The dilcovery of a few 

 living fpecies of cornua ammonis does not deftroy the 

 truth of this, for thefe ammonites are very different from 

 thofe which are found petrified. They are extremely rare, 

 and cannot be looked up to as the reprefentativcs of the 

 old ammonites, (b varied in their fpecies, and the number 

 of which in the .incient ocean was probably far more con- 

 fiderable than that of all the other ftiells befides." 



To every univalve (hell, rolled in a fpiral, fo as that 

 a horizontal plane will divide it into two equal parts, 

 fortned of united fpirals, and hearing a certain proportion 

 to each other, this author gives the name of an ammonite. 

 " I thought it abfoluttly neceflary," fays he, " to afcer- 

 tain the precife meaning of the term ammanite, previous to 

 defcribing that which I found during our voyage round 

 the world. The form of this is almoi't orbicular, the long 

 diameter being to the (hort one as three lines to two lines 

 and three quarters. A line is the twelfth part of an inch. 

 The firft fpire is by far the largeft, occupying nearly half 

 of the longitudinal diameter. The fummit is placed at 

 the diftance of about two-thirds of this diameter; it is 

 terminated on the right fide by a very fmall knob, vifible 

 only through a magnifier, rhns diftering from the ammo- 

 nite of Rimini, (mentioned in p. 22,) which befides is 

 microfeopical and celled, the inlide of this which we are 

 now fpcaking of being entirely plain. The number of 

 fpiral circumvolutions is four and a half; they are equally 

 convex on both fides, and are fixed on a plane, dividing 

 the (hell into two equal parts ; there is on each fide a kind 

 of bofs formed by the increafe of the perpendicular dia- 

 meter of the fpires, in proportion as they recede from the 

 center. The fuiface is linooth ; the back is armed with 

 a flat, even, brittle crelt, as thin as paper, furrounding it 

 on every fide like a ruft': it is about half a line bioad, 

 extends over the fummit of the i'pires, and ferves to join 

 them together. The mouth of the (hell is nearly trian- 

 gular; its edges projeft in the form of lips, and are rounded 

 at the border. I have often found this ammonite enclofed 

 in the ftomach of the (comber pelamis, or bonetta, caught 

 in the South Sea, between the tropics, where no bottom 

 was found with a line of more than two hundred fathoms. 

 Thele (hells were covered with a black clayey mud. Their 

 fize varies from one to four lines acrols; they are con- 

 fequently the largeft living ammonites that have yet been 

 dilcovered." 



The above reafoning, however, in fupport of the ex- 

 tindlion of the foflil ammonia, feems far from concluflve, 

 and by no means eftablifties the fa61 in quefhon. How 

 many fpecies of teftaceous animals have been lately difco- 

 vered, that have eluded the refearches of mankind for 

 thouliinds of years before ? and how many may yet re- 

 main in the depths of the ocean, totally unknown to man, 

 dwelling perhaps in a tranquil Itate, with the maturer 

 cornua ammonis ? That no fragments of thefe fliells in a 

 recent ftate are now ever found upon the fea-coafts of any 

 country, is no good argument to prove their non-exift- 

 ence; becaufe nothing lefs than a convulfion of the globe, 

 fufliciently powerful to overturn the bottom of the fea, 

 can call on fliore thefe pelagian fhells; for the fame parity 

 of re.rlbn that no convulfion of nature, lefs univerfal than 

 the general deluge, could have heaped up, promili:uoufly 

 together, the foflil fhells we now find on the moft elevated 

 fummits, and in fituations far removed from the places 

 of their natural and primeval abode. M. de Lamanon 

 feems anxious to prove, that the ancient ammonites did 

 not inhabit great depths of the fea; and that Linnaeus 

 was deceived when he fuppofed that in great depths they 

 may ftill be found. But this naturalift contradifts him- 

 fclf, and entirely does away his own argument, when he 

 tells us, that he could never find the recent ammonites 

 but in the South Sea, where no bottom was to be found 



with 



