62 Vertebrate Palaeontology of Cambridgeshire 



Chelonian remains are comparatively common in the 

 Cambridge Greensand. Part of a lower jaw in the British 

 Museum has been referred by the present writer 1 to the 

 existing genus Chelone, with the name C. jessoni; and another 

 specimen of the same part of the skeleton to the Tertiary 

 Lytoloma, as L. cantabrigiense*. Leathery turtles are indi- 

 cated by Protostega anglica 3 , assigned to an extinct genus 

 typically from Belgium. A lower jaw in the Sedgwick 

 Museum has been regarded by Prof. Seeley 4 as indicating 

 a land tortoise, and named, without description, Testudo 

 cantabrigiensis ; but there is little doubt that it does not 

 really belong to the existing genus. 



Of much greater interest are the small chelonian skulls 

 from the Cambridge Greensand which have been made the 

 type of the genus Rhinochelys*. Not improbably these 

 chelonians belong to the Pleurodira, a group in which the 

 head is retracted by a lateral flexure of the neck; with some 

 of the existing members of which they agree in having distinct 

 nasal bones. The temporal region of the skull is completely 

 roofed over by bone, as in turtles. The species R. pulchriceps, 

 R. cantabrigiensis^ R. macrorhina, R. elegans, R. brachyrhtmt, 

 and R. jessoni have been denned by the present writer. A 

 number of other specific names have however been assigned 

 by Prof. Seeley 6 to skulls in the Sedgwick Museum, but 

 since no descriptions are given it is unnecessary to quote them 

 seriatim. Fragments of chelonian shell from the Cambridge 

 Greensand showing a pustular external sculpture, have been 

 regarded as indicating a distinct genus and species, under the 

 name Trachydermochelys phlyctaenus but there is at present 

 no evidence to indicate that this type of shell does not pertain 

 to Rhinochelys' \ 



1 Cat. Foss. Eept. Brit. Mus. in. 36 (1889). 



3 Ibid. 68. 3 Ibid. 229. 



4 " Index to Ornithosauria, etc." xix. 



8 See Cat. Foss. Rept. Brit. Mus. in. 175. 

 8 "Index to Ornithosauria, etc." xvm. 

 7 See Cat. Foss. Rept. Brit. Mus. HI. 182. 



