PLESI0CHELYID.2E. 



187 



R. 1640. Slab showing the dorsal aspect of an immature carapace, 

 wanting the nuchal and all the marginals with the excep- 

 tion of two at the posterior extremity ; from the Purbeck 

 of Swanage, Dorsetshire. This specimen agrees with the 

 type carapace figured by Owen in his ' Wealden and 

 Purbeck Reptilia,' pt. i. pi. i., in that the 3rd neural 

 has a narrow junction with the 4th ; but the 8th costals 

 meet in the median line behind the 7th neural. The 

 vertebral shields are moreover somewhat wider, their 

 lateral borders having been situated on the vacuities 

 between the costal and marginal bones. This excessive 

 width of the vertebral shields at once serves to distinguish 

 this carapace from Acichelys, in which at a similar stage 

 of development these shields had their lateral borders 

 placed at some distance within the border of the ossified 

 costals. Purchased, 1889. 



24299. Slab showing the ventral surface of an immature carapace, 

 imperfect anteriorly, and wanting all the marginals ; from 

 the Purbeck of Swanage. This specimen closely resembles 

 the last. The neurals, with the exception of part of the 

 1st, are distinctly shown, and are seven in number ; the 

 3rd costals meet in the middle line behind the 3rd neural, 

 and the 8th costals behind the 7th neural. The imperfect 

 1st costal seems to have had the outer extremity of its rib 

 nearly as strongly developed as in the undermentioned 

 H. belli. Cunnington Collection. Purchased, 1849. 



23624. An imperfect shell ; from the Wealden of Burwash, Sussex. 



{Fig.) Noticed by G. A. Boulenger and the present writer in the 

 4 Geol. Mag.' dec. iii. vol. iv. p. 272, where it is provi- 

 sionally referred to Plesiochelys. In its long neural bones 

 and extremely wide vertebral shields the carapace (fig. 43) 

 agrees closely with the type; but the shields are even 

 relatively still wider. The meeting of the 3rd and the 

 8th costals is distinctly seen. The nuchal is imperfect, 

 but its shape accords with that of the type. The stoutness 

 of the extremity of the rib supporting the first costal (as 

 seen in section on the right side of the specimen) is 

 similar to that of H. belli. ' The plastron is well preserved, 

 although imperfect anteriorly. The narrow diamond- 

 shaped entoplastral resembles that of Idiochelys. The 

 absence of the mesoplastral (which at once serves to 



