148 CHELONIA. 



Genus THALASSEMYS, Rutimeyer 1 . 



Syn. Enaliochelys, Seeley 2 . 



Carapace moderately thick, flattened, with or without anterior 

 emargination, the costals well ossified, and the posterior neurals not 

 forming a tectiform ridge ; neurals more or less elongated, mostly 

 hexagonal, with short antero-lateral surfaces ; 5th neural with entire 

 postero-lateral border. Vertebral shields comparatively narrow, 

 with the underlying area devoid of flutings. Marginals appa- 

 rently wider than in Acichelys. Very large persistent vacuities in 

 the plastron. 



Thalassemys hugii, Rutimeyer 3 . 



Syn. Enaliochelys chelonia, Seeley 4 . 



The type species. Of very large dimensions, being the largest of 

 the Kimeridgian forms. Carapace very slightly emarginate ante- 

 riorly, with the 2nd, 3rd, and 4th vertebral shields narrowed in 

 front ; neurals long and narrow. 



Hob. Europe (Switzerland and England). 



R. 1645. Casts of several associated bones. The originals, which were 

 obtained from the Kimeridge Clay of Ely, Cambridgeshire, 

 are preserved in the Woodwardian Museum at Cambridge, 

 and are portions of the type of Enaliochelys chelonia, 

 which is noticed on p. 108 of Seeley's ' Index to Aves 

 &c. in Cambridge Museum.' The casts comprise the 3rd 

 (a), 5th (6), and 7th (c) neurals, an imperfect costal of the 

 right side (cl), and the crushed left femur (<?). The neurals 

 agree precisely with the corresponding bones of the type 

 carapace figured by Riitimeyer in the ' IST. Denkschr. schw. 

 Ges. Nat.' vol. xxv. art. 2, pi. i., but indicate a slightly 

 smaller individual. The femur precisely resembles 

 No. 46328 in contour, although of somewhat smaller size. 

 As arranged in the Cambridge Museum, the two femora 

 are described as the humeri, while the costals of the right 

 side are referred to the opposite side, and vice versa. The 

 costals. do not show the lateral sulci of the vertebral 

 shields. Made in the Museum, 1889. 



46326. The proximal portion of the fourth costal of the right side 

 of the carapace ; from the Kimeridge Clay of Devizes, 



1 Verh. schw. Ges. Nat. 1859, p. 57 ; also N. Denkschr. schw. Ges. Nat. vol. 

 xxv. art. 2, p. 27 (1873). 



2 Index to Aves &c. in Cambridge Museum, p. 108 (1869). — Insufficient de" 

 scription. 



3 N. Denkschr. schw. Ges. Nat. vol. xxv. art. 2, p. 27 (1873). 



4 Index to Aves &c. in Cambridge Museum, p. 10S (18G9). 



