STEEEOG-ENTS LIBYCA. 305 



at the inner angle of the mesoplastra [Ms.p.), which are thus wedged in between 

 marginals 5 and 6 and the outer ends of the hyo- and hypoplastra. The mesoplastra 

 are longer than broad ; the two inner borders are strongly convex. The borders of the 

 posterior lobe of the plastron are evenly curved to the posterior angles, except for 

 a slight notch where the furrow between the femoral and anal shields crosses the edge. 

 The sutures between the hypoplastra and the xiphiplastra {Xi.p.) run parallel Avith the 

 femoro-anal furrows and about 3 cm. in front of them. There is a deep rounded 

 notch 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 {g.) and the humerals {n.). Both 

 these plates are very small : the pectorals {pect.), on the other hand, are large ; 

 the suture between them and the abdominals runs across about 3 or 4 centimetres 

 behind the anterior end of the bridge. The limits of the abdominals, the femorals, 

 and the anals are shown in the figure. The bones constituting the posterior lobe 

 of the carapace have their upper surfaces raised into a ridge about 4'5 cm. from, and 

 parallel with, their outer borders ; from this ridge they slope away to the thin edge, the 

 sloping surface being evidently in great part covered by epidermal inguinal shields, 

 which seem to have extended back to the posterior ends of the xiphiplastra. 



The upper surface of the xiphiplastrals bears the bases of the pubes and ischia, 

 as is usual in the Pleurodira, and when the type specimen was found the whole 

 pelvis was in situ. The bases of the pubes are narrower and directed more forwards 

 than in Podocnemis, and the same is the case to a less degree with the bases of the 

 ischia. 



The ilium is short and stout ; it does not seem to have been much expanded at its 

 upper end. In the middle of the shaft the bone has a flat antero-external surface and 

 a rounded postero-internal surface ; it forms the greater part of the acetabulum. The 

 pubis is flattened and united with the xiphiplastron by a long narrow base ; the anterior 

 process is shorter than in Podocnemis. The ischium seems to have been slender, 

 but the greater part is missing. The acetabulum is roughly triangular, one of the 

 rounded angles being borne by each of the bones composing it, the angle on the pubis 

 being the most strongly marked. The ilium forms about two-thirds of the cavity, 

 the ischium constituting rather less than half of the remainder. The ilium of 

 Stereogenys podocnemioides figured by Reinach is very similar. 



R. 3039. Nearly complete carapace and plastron. Type specimen described and figured in Ann. 

 & Miig. Nat. Hist. [7] vol. xi. pp. 115-119, pi. vii. (reproduced in text-tig. 97). The 

 dimensions (in centimetres) of this specimen are : — 



Length of carapace in middle line 41-5 



Approximate width of shell 32 



Length of nuchal bone (in middle line) 5-7 



"Width of nuchal bone 7'o 



2r 



