chelonid^:. 49 



neurals are wanting, agrees in general shape and in the 

 contour of the wide vertebral shields with the type shell 

 figured by Owen in his ' Reptilia of the London Clay, 

 &c.' pi. vii. Bowerbank Collection. Purchased, 1865. 



37718. A smaller and more imperfect shell of the same general 

 type. The wide vertebral shields are well shown, and 

 the condition of the neuro-costal sutures both in this and 

 the preceding specimen is indicative of immaturity. 



Bell Collection. Purchased, 1863. 



26134 a. The imperfect carapace, with the right costals crushed 

 {Fig.) downwards and inwards so as to conceal the plastron; 

 from the London Clay of Bognor, Sussex. The type of 

 Chelone declivis. Figured by Owen, op. cit. pi. xiv., and 

 also in Dixon's ' Geology of Sussex,' p. 229, woodcut. The 

 narrower vertebral shields of this specimen are probably 

 due to its greater age. 



Dixon Collection. Purchased, 1851. 



28767. A nodule showing the dorsal aspect of the imperfect carapace 

 of a young individual : from Sheppey. 



Bowerbank Collection. 



35717. An imperfect carapace agreeing closely with No. 37718. 

 This specimen has been somewhat flattened by pressure. 



Purchased, 1860. 



Genus THALASSOCHELYS, Fitzinger \ 



Skull broader and shorter than in Chelone, with the orbits nearly 

 vertical, the nares directed somewhat upwards, a very wide inter- 

 orbital bar, and an occipital shield. Palate short, with thick low 

 alveolar walls and typically no ridge 2 ; pterygoids of moderate 

 length, slightly emargin ate, with the ectopterygoid processes a short 

 distance above their antero-external angles. Palatal apertures of 

 temporal fossae longer than wide ; posterior nares in anterior half 

 of cranium ; vomer short and usually not reaching the premaxillse. 

 Mandibular symphysis comparatively long, convex inferiorly and 

 concave superiorly, and typically without an oral ridge 2 . Shell 

 cordiform, with five costal shields, and the vacuities more or less 



1 Ann. Mus. Wien, vol. i p. 121 (1835). 



2 T. kempi is described as having oral ridges ; see Boulenger, ' Catalogue of 

 Chelonians, &c.' p. 186. 



PART ni. E 



