TESTUDO NEBR ASCENSIS. 567 



TESTUDO NEBRASCENSIS. Leidy. 



(Tab. xii. a, figs. 1, 2.) 



Stylemys Nebrascensis : Vr. Ac. Nat. Sci., vol. v. 172. 

 Tcstudo Nebrascensis: ib., vol. vi., 59. 



This species was first characterized as belonging to a new genus, under the suppo- 

 sition that the processes which rise upwards from the sternum to aid in the support 

 of the carapace were distinct bones, a mistake which arose from their unusual size 

 and prominence, and their being detached hy fracture from the sternum. 



In Dr. Owen's collection, there are two specimens of this species, varying in size, 

 and in some degree in minute anatomical detail. Both have the marginal plates 

 l)roken away in front and behind, and the larger has lost nearly all its carapace, 

 and the smaller the anterior portion of the sternum. The carapace of the smaller 

 specimen has a vertebral plate in excess introduced between the eighth and the V- 

 shaped plate. 



The species is more depressed than the Gophir, and has more the form of the 

 Emydes than the Testudines. The sternum is flat, and the axillary and inguinal 

 notches are directed downwards. 



The marginal plates are quite oblique above, and turn abruptly under at their 

 lower third. The bones are relatively thick and strong. 



In the smaller specimen the first vertebral plate is ten lines long and six broad. 

 Those from the second to the eighth inclusive are hexahedral ; the anterior four 

 being the larger and nearly equal in size. The ninth or accessory plate is trans- 

 versely oblong, quadrilateral. 



Each vertebral plate after the first to the eighth inclusive, articulates with two 

 pairs of costal plates. 



The first costal plate externally articulates with the first to the third marginal 

 plates, but does not quite reach the fourth. The vertebral scutes from the second 

 to the fourth inclusive, are hexahedral, and broader than long. 



The sternum agrees in its characters in both specimens, except in the smaller, the 

 anterior border of the humeral scute courses along the posterior edge of the axilla, 

 whereas, in the larger, at its external part, it turns forwards and outwards to the 

 axilla. 



The entosternal plate is pyriform, and is longer than it is broad, and encroaches 

 upon the position of the gular scutes. 



In the larger specimen the episternals are one and a half inches long. The 

 hyosternals are two and a quarter inches long, and articulate with the third to the 

 fifth marginal plate inclusive. 



The hyposternals articulate with the fifth to the seventh marginal plates. 



The gular scutes are angular posteriorly. The humeral scutes internally are six 

 lines long, and externally expand before and behind, and join the axillary and the 

 fourth and fifth marginal scutes. 



