INTEODUCTION. xv 



The ventral ribs seem to have been strongly developed and a number of widely 

 open V-shaped elements of the middle row can be seen ; they are fairly stout and well 

 ossified. There was probably at least one pair of lateral elements in the form of 

 short rods. 



The outline of the soft parts of the body seems to be indicated by a yellow stain, 

 best seen in the caudal region. The terminal caudal fin, however, is not only 

 outlined in this way, but also stands in slight relief as a natural cast, the anterior 

 border being especially clear (see text-fig. A, p. xii). The exact form of this region is, 

 however, somewhat obscured by the circumstance that the downwardly flexed portion 

 of the vertebral column has been somewhat straightened out into line with the anterior 

 part of the tail, in consequence of the curved position in which the animal is lying. 



In a few places on the ventral side the surface is covered by some patches of a thin 

 layer of a peculiar fibrous-looking substance. This has been examined in detail by 

 v. Amnion, who regards it as phosphatized muscle. The possibility that muscle may 

 be preserved in this way has been demonstrated by Reis * in several papers, but at the 

 same time the uniform thinness of the substance rather suggests that it may be 

 fossilized remnants of the skin which had fallen more or less into longitudinal 

 wrinkles. So long ago as 1860 von Meyer f noticed the presence of what he con- 

 sidered to be skin in a specimen of the present species, also from the Solenhofen 

 Lithographic Limestone. 



On the question of the origin of the Crocodilia, the Oxford Clay specimens throw 

 no light. The Steneosaurs are no doubt derived from tne various species of Mystrio- 

 saurus found in the Lias, but beyond that their descent cannot be traced. In the case 

 of the Geosauridse the early history is still more obscure. The only form anterior to 

 the Oxford Clay which appears to be nearly related is Teleidosaurus, of which 

 Deslongchamps J has described two species (T. cahadosi and T.joberti) and Collot § 



* See especially: " Untersuchungeu iiber die Petrificirung der Muskulatur," Archiv f. Mikros. Auatomie, 

 vol. xli. (1893) p. 492; and " iNeues iiber petrifk-irte Muskulatur etc." op. tit. vol. lii. (1S93) p. 262. 

 E. Traas has also written on the subject : see " Ueber die Einue von Ichthyosaurus" Jahreshefte Ver. 

 Vaterlaud. Naturkunde in Wiirttemberg, vol. xliv. (1888) p. 293; and "Die Hautbedeckung von 

 Ichthyosaurus" op. tit. vol. 1. (1894) p. 493. 



t "Fauna der Vorwelt," Eept. Litb. Schiefer, p. 96, pi. xv. 



X ' Notes Paleontologiques,' p. 274. 



§ " Eeptile Jurassique (Teleidosaurus gaudryi) trouve a, Sainte-Seine lAbbaye (C6te-d'Or)," : Mem. 

 Academie Dijon, [4] vol. x. (1906) p. 41. 



