224 



The ninth plate appears like a correspoiuling pair of costal plates connate 

 in the median line. The tenth plate is lozenge-shaped, and occupies a 

 similar shaped interval of the ninth vex'tebral and the pygal plates. 



The eight pairs of costal plates in their alternate narrowing and widening 

 toward the extremities resemble those of the living tortoises, though the 

 variation is not so great as usual in these. 



The interior of the vertebral plates of Styleuiys exhibits a deep, narrow, 

 keel-like ridge, as represented in Fig. 6, Plate III, and Fig. 9, Plate XIX, in- 

 tended for union with the neural arches of the vertebrae. A similar con- 

 dition exists in the Gallipagos and other living tortoises. 



The costal capituli, as seen in Fig. 6, Plate III, and Fig. 9, Plate XIX, 

 are feebly developed as in most species of Testudo, but are not reduced to 

 the rudimental condition observed in our gopher. 



The first pair are as well developed as usual. The sixth and seventh pairs 

 unite with processes of the corresponding vertebral plates. The eighth and 

 ninth pairs, better developed than those in advance, unite in the root of the 

 process of the eighth costal plate for the attachment of the pelvis. 



The scutes of both the carapace and plastron of Stylemys correspond with 

 those of Testudo. The pygal scute is single as in all living tortoises, except 

 Manouria. The pectoral scutes are very narrow, as usual in Testudo. 



The thickness and strength of the shell of Stylemys is greater than ordi- 

 narily in the latter, liut proportionately not more so than in several living 

 species. 



The bones of the limbs, so far as we are acquainted with them, approach 

 in character those of the tortoises. The concavity above the articular surface 

 of the distal extremity of the humerus, but especially of the femur, is deeper 

 than in the living forms. 



The remains of Stylemys are apparently referable to three species, all 

 geographically and perhaps geologically separated. 



Stylemys nebrascensis. 



The remains of this species form one of the most abundant fossils of the 

 Miocene Tertiary deposit of the Mauvaises Terres of White River, Dakota. 

 A multitude of specimens of nearly entire shells have been collected by all 

 explorers of the locality in which they are found. Tliey present a great 



