ACICHELYID^. 155 



41234. A nearly similar specimen of the fifth neural bone ; from 

 Weymouth. Purchased, 1868. 



41234 a. The fifth neural bone of an immature iudividual ; from 

 Weymouth. The sulcus of the vertebral shield is abraded. 



Purchased, 1868. 



44178 a. A neural bone, probably the seventh, of an immature in- 

 dividual ; from Weymouth. Purchased, 1873. 



44177 C. A costal bone, probably the third of the left side of No. 

 44177 ; from Weymouth. Purchased, 1873. 



Genus non clet. 



The undermentioned costals are characterized by the fluting ex- 

 tending over the whole of the proximal portion of the bone, in place 

 of being confined to the periphery of the areas occupied by the 

 vertebral shields, as in the type of Pelobatoclielys. Some of the 

 figured specimens of Acichelys approximate to this arrangement of 

 the sculpture. 



41403. The proximal portion of a small and probably immature 

 costal ; from the Kimeridge Clay of Weymouth, Dorset- 

 shire. Purchased, 1869. 



R. 900. The proximal portion of a much larger costal : from the 

 Wealden of the Isle of Wight. 



Fox Collection. Purchased, 1882. 



R. 900 a. Fragment of a similar costal ; from the Wealden of the 

 Isle of Wight. Fooc Collection. 



R. 290. Fragment of a similar costal, in matrix ; from the Wealden 

 (Hastings group), locality unknown. 



Egerton Collection. Purchased, 1882. 



Genus TROPIDEMYS, Butimeyer \ 



Carapace with the costals well ossified, and the neurals extremely 

 thick ; neurals (fig. 38) with the antero- and postero-lateral sur- 

 faces subequal, and in the posterior region of the carapace forming a 

 tectiform ridge, with a chevron-like (ft) cross-section ; 5th neural 

 not laterally emarginate. Vertebral shields narrow, with the un- 

 derlying areas smooth. Plastral vacuity tendiug to obliterate more 

 or less completely. 



1 IS. Denkschr. scliw. Ges. Nat. vol. xxv. art. 2, p. 27 (1873). 



