ICHTHYOSAURUS. 



ICHTHYOSAURUS. 



cfl*n.wUhtb*restoftbe akrietoo, would 

 UtW by tb* dene* exterior integument, until 

 ,,aris**s oY tb* abdomen at *om* yielding P| 



1 continue to bo bald 



until the rupture of the 



J yWdtag point had *et free the 



nees r'- J by putrefcctioa; and tbe skeleton, baring undcr- 



rosw cerUin partial dislocations, from the decomposition of the more 



\tfMmg licamonU, would subside to tbe bottom, and become 



imbedded in the esdimenUry deposits, exhibiting the fracture of tbe 



tail alluded to. 



Treatise' (pL 14), wbich shows a Urge mass of Gh scales, chiefly 

 refvmble to tbe I'holidophorut limbatiu, intermingled with coprolitet 

 Ihroughout the entire region of the ribs, and in the more matured 

 coprolites themselves. Dr. Buckland, to whom we are indebted for 

 the hUtory of these curious bodies, says, speaking of the intestinal 

 canal of the Jcklkyotauri :" Besides tbe spiral structure and conse- 

 quent shortness of the small intestine, we have additional evidence to 

 show even the form of the iniuuto vessels and folds of the mucous 



With respect to tbe relative position of this conjectured caudal 

 tegunwnUry fin of tbe ItUkyotaunu, Professor Owen could not 

 perceive any indication of its horizontally in the forms of the 

 vcrtsbnr which he supposes to have supported it ; and he regards the 

 snperaddition of posterior paddles in these air-breathing marine 

 .p'py.1. u a compensation for the absence of that form of fin which 

 is so essential in the Cttacta, for tbe purpose of bringing the head to 

 tbe surface of tbe sea to inhale the air. On the other hand a vertical 

 caudal fin senna especially required by the short-necked and stiff- 

 necked SrAlAyoMHri, in order to produce with sufficient rapidity the 

 lateral movements of the head, which were needed by those predatory 

 inhabitants of tbe ancient deep ; while in the flaiosaurus such a fin 

 would be unneoanary, in consequence of the length and mobility of the 

 neck ; and Professor Owen concluded by stating, that in those skeletons 

 of Pltiatmri in which the till is perfect it is straight, and presents 

 no indication of tbe partial fracture or bend which is so common in 

 the tails of ItkOiyotauH. 



Figure* of tbe tails of five specimens of Icutliyonauri , belonging to 

 tbe species /. comnttnu, I. tcnuirottrit, and /. inlcrmcdiut, accompanied 



Professor Owen ha* since ascertained that the terminal caudal verte- 

 bra of tbe /cUlyotaunu are compressed or flattened from side to side 

 in a remarkable degree ; a circumstance, he observes, confirming the 

 accuracy of tbe conjecture of tbe verticality of the caudal fin, and the 

 best proof perhaps of its actual presence in the living animal. 



That the /dUAyosf enjoyed the sense of smelling in a consider- 

 able degree can hardly be doubted from the structure and position 

 of the nostrils, nor is there any reason for supposing that they were 

 not gifted with the sense of taste ; but their power of vision must 

 have been great, and indeed Dr. Buckland justly speaks of tbe enor- 

 mous magnitude of the eye as very much exceeding that of any living 

 animal, and as being the most extraordinary feature of the head. He 

 allude* to a skull of feklkyotaarui platyodon in the collection of Mr. 

 Johnson at Bristol, and remarks that in this specimen the longer 

 diameter of tbe orbital cavity measures fourteen inches. The eye has, 

 as Mr. Cooybeara remarks, its sclerotic* composed of a bony or rather 

 scaly substance, subdivided into thirteen plates, a* will be seen in the 

 eat (cob. 801 , 202), where two of these plate* are represented separately. 

 Mr. Conybean, in tbe passage to which we have referred, goes on to 

 date that be had then before him the eye of a middle-sized lizard from 

 Germany, which ban a structure exactly similar, excepting that the 

 plates w*r* more numerous : this, he states, was pointed out to him 

 by tb. UU Mr. Miller; and he adds that the Chameleon and Jyuana 

 hv, simitar osseous laminc, as has tbe Tortoise, but that in this latter 

 animal they form, as in birds, the anterior disc. This conformation 

 was highly important to the adjustment of an organ whose functions 

 were demaodVd both above and below the surface of the water. 

 [Bum.] Tb* araa* of hearing appears to have been sufficiently 

 developed, and that of touch was probably about upon a par with 

 tbe sensation* of tb* modern cetaceans. 



An normous expansion of the jaws, which were so constructed as 

 to bear tb* shock of tbe most violent collision, and were furnished 

 with a constant (accession of teeth, formed an organ of seizure well 

 feted to tb* voracity of an animal that not only preyed upon fishes 

 and other marine animals, but, like tbe ravenous pike of our fresh- 

 waters, fed upon it* own congeners and even species. The prey was 

 d into a stomach, which must have been nearly co-cxtensi' 

 eavity of tbe body, ami tbe contents were thence mode 



with tb* car 



pass through an intestinal canal which appears to have resembled, as 

 Dr. Hoeklsad observes, the spiral intestines of some of the swiftest 

 sad most voracious of our modrm finite*. 



Tb* evidence apon which this ascertion is mad* h to be found in 

 various speoimcM, like that in tbe Oxford Museum, from the lias at 

 Lyme Hefts, and ftgnnd by Dr. Buckland in his 'Bridgowater 



Dr. Bnckland. 



membrane by which, it wan lined. This evidence consults in a series 

 of vascular impressions and corrugations on tho surface of the copro- 

 lite, which it could only have received during Ha passage through the 

 windings of this flat tube. If we attempt to discover a final cause 

 for these curious provisions in the bowels of the extinct reptile inha- 

 bitants of the seas of a former world, we shall find it to be the same 

 that explains the existence of a similar structure in the modern 

 voracious tribes of sharks aud dog-fishes. As the peculiar voracity of 

 all these nnimals required the stomach to be both large and long, 

 there would remain but little space for the smaller viscera ; these are 

 therefore reduced, as we have seen, nearly to the state of a flattened 

 tube, coiled like a corkscrew around itself; their bulk is thus mate- 

 rially diminished, whilst the amount of absorbing surface remains 

 almost the same as if they had been circular. Had a large expansion 

 of intestines been supcnulded to the enormous stomach and lungs of 

 the Ichlhyoaaurtu, the consequent enlargement of tho body would 

 have diminished the power of progressive motion, to the great detri- 

 ment of an animal which depended on its speed for tbe capture of it* 

 prey. The above facts, which we have elicited from the coprolitio 

 remains of the Ichtliyosauri, afford a new and curious contribution to 

 our knowledge both of the anatomy and habits of the extinct inhabit- 

 ants of our planet. We have found evidence which enables us to point 

 out the existence of beneficial arrangements and compensations even 

 in those perishable yet important parts which formed their organs of 

 digestion. We have ascertained the nature of their food and the 

 form and structure of their intestinal canal ; and have traced the 

 digestive organs through three distinct stages of descent, from a largo 

 and long stomach, through tho spiral coils of a compressed ileum, to 

 their termination in a cloaca, from which the coprolites descended 

 into the mud of tho nascent lias. In this lias they have been in' 

 during countless ages, until summoned from its deep recesses by tin- 

 labours of the geologist to give evidence of events that passed at the 

 bottom of the ancient seas in ages long preceding the existence of 

 man." (' Bridgewater Treatise.') 



Coprollte of Mthyoiniirtu, Dr. Buckland. 



a, Mnimifiril ml" of Phalidvpltoriu limlatui imbedded therein (internal view) ; 

 , external Tiew of tbe tame. 



The external integument appears to have been a simple naked skin 

 unprotected by any defi-nci- ; it pmbiibly resembled in some degree 

 tho dermal covering of tho cetaceans. 



The structure of these reptiles have been sometimes referred to us 



