Pleurodiran Chelonians from Ejypt. 119 



S. Cromeri in tlie narrower form of the shell and the diflfereut 

 shape of the entoplastron ; moreover, the beds in which it is 

 found are much later, and all the species of mammals in them 

 are different from those occurring in the lower beds. 



Tiie small development of the buttresses compared with those 

 found in Podocnemis and other recent Pleurodirans, as well 

 as the form and the thickening of the anterior portion of the 

 plastron, may indicate that this species and that next described 

 were more terrestrial in their habits than the modern members 

 of the group. 



The dimensions of the type specimen of Stereogenys I'lbyca 

 are : — 



centim. 



Length of carapace in the middle line 41 "5 



Greatest length of plastron 40 



Length of plastron in middle line 36-5 



Width of anterior lobe of plastron 17"4 



„ posterior „ „ 20-5 



Length of bridge 17'7 



Approximate width of shell ^2 



Stereogenys Cromeri, Andrews *. (PI. VIII. fig. 1, A& B.) 



The specimens from the Middle Eocene just mentioned as 

 being referred to Stereogenys Cromeri — a species f )unded on 

 a skull and mandible — were collected last year by Mr. H.J. L. 

 Beadnell and myself in the neighbourhood of Qasr-el-Sagha 

 (Schweinfurth's Temple). Portions of the shell of this 

 Chelonian are, like the fragmentary skulls, common in these 

 beds, and in one case a nearly complete^ tliough somewhat 

 crushed, shell was found ; this specimen is here described. 

 It is unfortunate that in these deposits the shells are usually 

 more or less tidckly coated with gypsum and other substances, 

 which greatly obscure and often entirely conceal the lines of 

 division between the various plates and shields. 



In the nearly complete shell the carapace has been to some 

 extent flattened and, at the same time, widened by pressure. 

 Its dimensions in its present state are : — Length in a straiglit 

 line 46'5 centim., width 41'5. 



The Carap ice (Pi. VIII. fig. 1, A). — The number of neural 

 bones cannot be determined, but it seems certain that, as in 

 the last species, the neural series is separated both from the 

 nuchal and pygal bones by the junction in the middle line of 

 the anterior and posterior pair of costals respectively. There 

 are eiglit pairs of costal plates, but the number of marginals 



* "Preliminary Note on some recently discovered Extinct Vertebrates 

 from Egvpt. (Part II.)" Geological Alagazine, dec. iv. vol. viii. (1901), 

 p. 442. 



