122 On some Pleurodiran Chelonians from Ecjypf. 



from Stereogenys libyca in the arrangement of the epidermal 

 shields of the plastron, the anterior portion of which is shown 

 in the figure. It will be seen that the intergular shield (Jg.) 

 is very small, and instead of separating both the gular {q.) 

 and humeral (n.) shields, it does not even completely separate 

 the gulars, which meet in the middle line for some distance. 

 The entoplastron is also different from that of S. libyca, being 

 a diamond-shaped bone. There is a small laterally-placed 

 mesoplastron. As far as at present known, there seems to 

 be no reason for not referring this Chelonian to the genus 

 PodocnemiSy and the name Podoctiemis fajumensis may be 

 adopted for it. The specimen figured was collected by 

 Mr. Beadnell in the season of 1902. 



The approximate width of the plastron figured, immediately 

 in front of the bridge, is 11'5 centim. 



The Chelonian fauna of the Middle and Upper Eocene beds 

 of the Fayum seems to be a very rich one, for, although the 

 region is still very imperfectly known, a considerable number 

 of species, including representatives of all the main groups, 

 have already been discovered. From the Middle Eocene we 

 have PsephopJiorus eocceniis, T/talassochelys h'byca, Stereo- 

 genys Cromerij and Podocnemis cmtiqua, which occur asso- 

 ciated with the mammalian genera Moeritherium, Barytherium, 

 Eosiren, and Zeughdon^ and with tiie Ophidians Gigantophis 

 and Pierosphenus (Mosriophis). From the Upper Eocene in 

 addition to Stereogenys libyca and Podocnemis fajumensis 

 there is a gigantic land-tortoise, apparently allied to Testado 

 perpiniana, Deperet, which will be described elsewhere; 

 associated with these Chelonians occur remains of Palceo- 

 mastodon, Arsinoitherium, Phiomia^ Sagkatherium, &c. 



EXPLANATION OF THE PLATES. 



Plate VII. 



Stereogenys libyca {ty-^Q specimen). A, carapace; B, plastron; C, right 

 side of shell. About \ natural size. 



Plate VIII. 



Fig.'i. Stereogenys Cronieri. A, carapace ; B, plastron. About J uatural 



size. 

 Fig. 2, A & B. Podocnemis antiqtia (type specimen). A, carapace ; B, 



plastron. About 5 natural size. 

 Fig. 2, C. Podocnemis fajumensis (type specimen). Anterior portion of 



plastron. 5 natural size. 



Ent., entoplastron ; Ep., epiplastral ; Hy.p., hyoplastral ; Ilyp.p., hypo- 

 plastral ; A?*., nuchal bone ; Ms.p., mesoplastral ; Pyg., suprapygal ; 

 Xi.p., xiphiplastral ; g., gular shield ; ig., intergular shield : n., humeral 

 shield ; p., pectoral shield ; v., vertebral shield. 



