PLESIOCHELYIDiE. 



185 



Meyer's ' Rept. Lith. Schiefer,' pi. xviii. fig. 1, showing no neurals 

 posteriorly to the third costals. 



Hah. Europe (Bavaria and France). 



40346. Cast of a slab showing the dorsal aspect of the imperfect 

 skeleton of an immature individual. The original was 

 obtained from the Lower Kimeridgian Lithographic Stone 

 of Cirin (Ain), and is preserved in the Museum at Lyons ; 

 it is the type of Chelonemys ovata, and is figured by Biiti- 

 meyer in the ' N. Denkschr. schw. Ges. Nat.' vol. xxv. art. 2, 

 pi. xv. fig. A. There appear to have been seven neurals. 

 The great width of the skull, as compared with that of 

 the next example, appears to be due to crushing. The 

 lateral flexure of the neck in this and the other two speci- 

 mens figured in the same plate is strongly in favour of 

 Pleurodiran affinities. Purchased, 1867. 



40345. Cast of a slab exhibiting the ventral aspect of an apparently 

 similar skeleton. The original, which was obtained from 

 the Lithographic Stone of Cirin, and is preserved in the 

 Museum of Lyons, is the type of Clielonemys plana. It is 

 figured by Riitimeyer, op. cit. pi. xv. fig. B. 



Purchased, 1867. 



Genus HYLJEOCHELYS, Lydekker \ 

 Syn. (?) Plastremys, Owen 2 . 



Shell with distinctly emarginate nuchal ; neurals long and 

 narrow, usually only seven in number, with the 8th costals meeting 

 in the middle line ; entoplastral narrow and diamond-shaped ; 

 hypoplastics short. Vertebral shields very broad, with the under- 

 lying areas either smooth or slightly fluted ; inframarginals broad 

 and extending on to the marginal bones ; sulcus between abdominal 

 and femoral shields as in Plesiochelys. 



The dorsal ribs are usually strongly developed, the rib underlying 

 the first costal being, as in Idioclielys, very prominent. The width 

 of the vertebral shields of the carapace always exceeds twice their 

 length, and may be more than three times the length. The shell is 

 of moderate thickness, and may have a persistent plastral vacuity. 



1 Quart. Journ. Geol. Soc. vol. xlv. p. 513 (1889). 



2 Ibid. vol. xxxTii. p. 370 (1881). 



