1S70.] ^^9 [Cope. 



.t^roove inside near the bridge, but it descends abruptly :it the median 

 xii)liisternal suture behind. The anterior extremity of the plastron is 

 rather broadly truncate, but little excavated, and with thick margin. The 

 form of the mesosternum is easily made out, from the fact of the pres- 

 ervation of at least one of all its corresponding marginal sutures. Its 

 antero-posterior length is at least .75 less than its transverse. It had no 

 posterior median process or spine, as in many Emydes. 



As regards the scuta, the femoro-anal suture is directed backwards out- 

 wardly; the abdominal scuta are the longest. The pectorals, instead of 

 narrowing medially, as in most Cryptodira, widen interiorly, their com- 

 mon anterior apex being on the mesosternal bone. The gulars are much 

 reduced by the large intergular ; each forms a spherical triangle — the 

 apex outwards, the suture with the humeral, concave. The intergular is 

 marginal, behind as wide as before, and convex; each half .66 wide as 

 long. 



The plastron is everywhere quite thick medially, but less so than in the 

 A. pectoralis. The superior surface of the xiphisternal bone presents a 

 citrved ridge in the position of the pubic scar of the Pleurodira, which is 

 nearer the margin than either suture, and slightly curved backwards. A 

 marked sublongitudinal depression is seen between it and the median 

 suture. Kear the latter, more than one-fourth its length from the 

 margin, thus farther from the latter than in Taphrosphys sp., is a smooth, 

 low knob corresponding to the ischium. 



The posterior lobe of the plastron is broad and regularly rounded, re- 

 sembling thus the A. agilis. In the latter the pelvic ridges are scarcely 

 developed at all, and the bone is everywhere thinner. 



The axillary margin within presents a strong ridge, which becomes 

 elevated as it rises with the axillary internal buttress of the carapace. 

 This ridge is much weaker in A. beatus and the other species. The ex- 

 ternal surface of the bones is studded with impressed dots, which are 

 separated by intervals posteriorly, but on the episternal bone are con- 

 fluent, leaving the surface rugose with small elevations. The sculpture 

 differs from that of A. agilis in being minuter, less distinct, and not dis- 

 posed in regular rows. The fragment of the bridge displays the axillary 

 and part of the anterior intermarginal plate. The former extends con- 

 siderably in front of exterior to the axillary notch ; the latter can only 

 be compared with the same in A. pectoralis, as it is not preserved in the 

 A. agilis. It is relatively broader than in the foimer, and with less 

 oblique anterior border ; the exterior angle which joins the suture of the 

 marginal is situated more anteriorly. A considerable extent of a mar- 

 ginal scutum of the bridge is preserved. Its transverse exceeds its longi- 

 tudinal extent, and its anterior margin is regularly convex. 



One costal presents a rudiment of capitulum ; the other none. 



M. 

 Length of plastron 0.484 



Width " to first marginal of bridge 0.33 



Width posterior lobe at groin 0.23 



