216 CHELONIA. 



woodcut. The pyriform shape of the intergular shield is 

 distinctly shown. The transverse diameter of the ento- 

 plastral only very slightly exceeds the vertical. The 

 inframarginal shields differ somewhat in their mode of 

 arrangement from those of the type specimen of the so- 

 called P. eoncinnum, but this is not necessarily a specific 

 character. Presented by B. Bright, Esq., 1874. 



Genus PLATYCHELYS, Wagner 1 . ■ 



Syn. Helemys, Riitimeyer 2 . 



Carapace somewhat depressed, with a number of more or less 

 distinct ridges or prominences on the neurals and costals. Neurals 

 short and of irregular contour, the width usually much exceeding 

 the length. Bridge short. Mesoplastrals not meeting in the middle 

 line. Vertebral shields much wider than long ; a nuchal shield ; 

 intergular undivided 3 . No articulation between pelvis and plastron. 



Platychelys oberndorferi, Wagner 4 . 

 Syn. Helemys serrata, Riitimeyer 5 . 



The type species. Length of carapace averaging 0,241 (9*5 inches). 

 Carapace subcordiform ; neural bones without continuous median 

 keel; neurals and costals of same approximate antero-posterior 

 diameter, and consequently each neural articulating chiefly with its 

 corresponding costals. Prominences on carapace very strongly de- 

 veloped, and the posterior border of the latter serrated. 



Hob. Europe (Bavaria and France). 



49156. Cast of a slab exhibiting the dorsal aspect of the nearly 

 entire carapace. The original was obtained from the Lower 

 Kimeridgian Lithographic limestone of Kelheim, Bavaria, 

 and is preserved in the Museum at Munich. It is figured 

 by Wagner in the ' Abh. k. bay. Ak. Wiss.' vol. ix. pt. i. 

 pi. i., from which figure the accompanying woodcut is 

 reduced. Other specimens are figured by Riitimeyer in 

 the ' N. Denksch. schw. Ges. Nat.' vol. xxii. art. 5, pis. 

 iii., iv. (1867), which show that the form of the neural 

 bones is subject to variation, and also exhibit the struc- 

 ture of the plastron. Purchased, 1878. 



1 Abh. k. bay. Ak. Wiss. vol. vii. pt. i. p. 242 (1853). 



2 Verb. schw. Ges. Nat. 1859, p. 58. 



3 Vide Zittel, Palaeontographica, vol. xxiv. pi. xxviii. 



4 Loc, tit. 5 Loc. tit. 



