310 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.38. 



rior inner angle there is a notch for a pari of the border ol the ento- 

 plastron. Of the right hyoplastron there is present the outer and 

 anterior portion. The free border is rather obtuse. The sutural 

 edge for con tacl with the epiplastron remains, as well as that forunion 

 with the entoplastron. In the latter notch the hone is 4 mm. thick. 

 One can not be certain regarding the form ol the epiplastron. It is 

 not probable that there was any specially developed epiplastral lip. 

 There are on both hyoplastra traces of the humero-pectoral sulcus. 

 From the axillary notches it was directed inward and strongly for- 

 ward to cross the entoplastron, thus differing from that of Glyptqps. 

 The pectoro-abdominal sulcus crossed the plastron along the middle 

 of the niesoplastra. The abdomino-femoral sulcus starts behind the 

 l>;i>('^ of the inguinal buttresses and swings somewhat backward on 

 its way to the midline. The median sulcus of the plastron follows 

 closely the sutures between the bones of the two sides. In most of 

 the relatives of this species it runs a very irregular course. There 

 was probably a series of inframarginal scutes on each bridge, but 

 these do not appear on the specimen. 



Of the left first costal (Plate 10, (ig. 2) only the outer extremity is 

 missing. The articulation with the peripherals was by means of 

 dentated sutures. On the upper surface are parts of the first costal 

 scute and of the first and second vertebrals. As the width of neither 

 the nuchal nor the first neural bone is known it is impossible to deter- 

 mine accurately the width of the vertebral scutes represented. How- 

 ever, the first vertebral was considerably wider than the second. On 

 the inferior surface of the bone is seen the ridge produced by the 

 strongly developed rib, which forms an articulation with the axillary 

 buttress. This buttress rose about 10 mm. above the lower border 

 of this costal. 



The costals represented by fig. 3 of Plate 10 belong to the left side. 

 The one with the descending sulcus is probably the fourth from the 

 front ; and the next one, the fifth. These bones are about 3 mm. thick. 

 The vertebral scutes extended out about 10 mm. from the neural bor- 

 ders. \i is probable, therefore, that the vertebral scutes were not 

 far from 30 mm. wide. All the bones of the specimen are orna- 

 mented with low, (dose-set elevations, or pustules, of which there are 

 seven in a line 5 mm. long. Their summits are rounded and the val- 

 leys between thcin ,nc of moderate width. In 0. victa there is the 

 same number of pustules in a 5 mm. line, but they seem to have more 

 pointed summits and the intervening valleys are wider. In compari- 

 son with their width the bones of ('. /><irr<i are considerably thicker 

 than those of the type of C. victa. In ('. parva the vertebral scute 

 extends bej ond the neural border of the costal a. distance equal to the 

 width of the costal; in C. victa the vertebral extends outward a dis- 

 tance equal to only two-thirds the width of the costal. 



