PLESIOCHELYID^!. 189 



Hylseochelys emarginata (Owen *). 



Syn. Pleurosternum emarginatum, Owen 2 {in parte). 

 Platemys emarginata, Maack 3 . 



Imperfectly known, bnt attaining considerably larger dimensions 

 than the type species. Nuchal larger, narrower, and more deeply 

 emarginate than in the latter. Plastron probably with a very large 

 vacuity, which extends into the hyoplastral. 



This species was founded on a carapace from the Purbeck, of which 

 the exposed ventral aspect is figured by Owen in his ' Wealden and 

 Purbeck Reptilia,' pt. i. pi. iv. 4 From the deeply emarginate 

 nuchal and the strongly developed ribs there is no reasonable doubt 

 that the species should be referred to the present genus. If the 

 undermentioned plastron be rightly referred, this form will certainly 

 be specifically distinct from H. belli. 



Hab. Europe. 



R. 1522. Slab showing the ventral aspect of the nuchal bone ; from 

 the Purbeck of Swanage, Dorsetshire. This specimen 

 agrees with the corresponding bone of the type carapace, 

 exhibiting the same deep emargination, and the groove on 

 the ventral aspect of the anterior border. No history. 



45937. Slab exhibiting portions of a shell which from its large size 

 is probably referable to the present form ; from the Purbeck 

 of Swanage. This specimen shows the left half of the 

 greater part of the plastron, from the ventral aspect ; the 

 dorsal aspect of the 3rd left costal, and the ventral aspect 

 of the 6th costal of the same ; together with several mar- 

 ginals. The 3rd costal shows part of the sulcus of the 

 2nd vertebral shield ; which is thus seen to have had the 

 characteristic wide shape. The plastron agrees in general 

 characters with the specimens mentioned under the head 

 of H. belli, but the vacuity extends into the hyoplastral. 

 The marginals agree closely with the posterior ones of 

 that species. Presented by J. C. Robinson, Esq., 1874. 



1 Wealden and Purbeck Reptilia (Mon. Pal. Soc), pt. i. p. 6 (1853).— Pleu- 

 rosternum. 2 Loc. cit. 



3 Pakeontographica, vol. xviii. p. 293 (1869). 



4 The other specimens figured under the same name are referable to the 

 Pleurosternidce. 



