Pleurodiran Chelonians from Egypt. 117 



to; it is roughly triangular in outline, with rounded angles, and 

 is nearly the same shape as the overlying vertebral shield. 



There are tive vertebral shields (<;.),the anterior of which 

 is very narrow, much narrower than the underlying nuchal 

 bone ; in the recent Pelomedusa and Podocnemis, the only 

 genera it is necessary to consider in this connexion, the reverse 

 is the case. The remaining plates are roughly hexagonal, 

 the antero-lateral being slightly shorter than the postero- 

 lateral one. The posterior shield, as already mentioned, is 

 very convex ; it is nearly the same shape as the underlying 

 suprapygal, but much larger (see PI. VII. figs. A & C). The 

 costal shields are four in number, the marginals twelve. 

 There is no nuchal shield. On the anterior border of the 

 carapace the extent to which the marginals are exposed is 

 very small, but posteriorly, where the carapace is somewhat 

 expanded, the area is much greater. 



The Plastron (Pi. VII. fig. B).— The posterior lobe of the 

 plastron is wider than the anterior and the length of the 

 bridge is about the same as the widtli of the front lobe. 



The entoplaslron (Ent.) is a relatively small escutcheon- 

 shaped bone, from the outer angles of w^hich the sutures 

 between the epi- and Lyoplastra run forward at an angle 

 of about 45° with tlie long axis of the siiell and cut tlic 

 border of the plastron in the notch marking the end of the 

 groove between the humeral and pectoral shields. The 

 suture between the hyo- and hypoplastra {tly.p. and Hyp.p.) 

 crosses at the level of the middle of the bridge and ter- 

 minates externally at the inner angle of the mesoplastra 

 {Ms.p.)^ which are thus wedged in between the marginals 

 5 and 6 and the inner ends of the hyo- and hypoplastra. 

 The mesoplastra are considerably longer than broad. The 

 suture between the hypo- and xiphiplastra (Xi.p.) runs parallel 

 to and about 3 centim. in front of the groove between the 

 femoral and anal shields. There is a deep rounded n^tch 

 between the posterior ends of the xiphiplastrals. 



The intergular shield (ig.) is very large and extends back 

 as far as the middle of the entoplastron, separating both the 

 gulars and the humerals. This condition, as far as I know, 

 occurs in no other Pleurodiran except in the shell described 

 below and referred provisionally to Stereogenys Gromeri. 

 Both the gulars [g.) and the humerals {n.) are very small ; 

 the pectorals (pect.), on the other hand, are very large, the 

 suture between them and the abdominals runs across about 

 3 or 4 centim. behind the anterior end of the bridge. The 

 limits between the abdominals and the femorals and between 

 the latter and the auals are shown in the fi;;ure. 



