TESTUDINID&. 385 
standing Cope’s statement. Its length was about 110 mm. The scutal sulci are very obscure 
on this fragment of the plastron, but the gulo-humeral is distinguishable. 
An anterior peripheral has the upper surface nearly flat and the free border acute. The 
hinder peripherals (fig. 482) are strongly fared upward toward the free border, the ninth most 
so (fig. 484), the eleventh less so (fig. 485). The ninth has a width along the free border of 
85 mm. and the height was about go mm. in a straight line. All the peripherals have a thick- 
ness of about 18 mm. The pygal is 21 mm. thick. 
Cope states that the sulci are deeply imprest. Those of the carapace are distinct enough, 
but those of the front of the carapace are very narrow, shallow, and indistinct. The gulo- 
humeral sulcus is very narrow and shallow and distinguisht with difficulty. 
Osborn, Scott, and Speir’s identification of this species is based entirely on two ungual 
phalanges collected by them in the Bridger beds. 
Genus STYLEMYS Leidy. 
Testudinide with the plastron joined to the carapace by sutures, and with inguinal 
buttresses which pass a short distance within the carapace between the fifth and sixth costal 
plates. No hinge in either plastron or carapace. Of the neural plates, those behind the third 
are hexagonal and have the antero-lateral sides much the shortest. The second and third may 
be hexagonal; or the second may be octagonal and the third tetragonal. ‘Two or three supra- 
pygals; the penultimate, bifurcate. Rike at distal ends of otal plates entering pits in 
peripherals of bridges. Costal plates with opposite ends differing much or little in width. 
Fpiplastral lip not projecting beyond the general contour of the anterior lobe of plastron. 
Entoplastron in front of the humero-pectoral sulcus. Supracaudal scute single. Skull and 
limbs, so far as known, like those of Gopherus. 
Type: Stylemys nebrascensts Leidy. 
The relationship of this genus has been variously regarded. It was establisht by Leidy, 
the name being given through a misconception that the plastral buttresses were separate 
bones. On the: discovery of his error Dr. Leidy employed for a while the name Testudo for 
the species of this genus, while in his latest work on the genus (Contrib. Ext. Fauna West. 
Terrs. ) he vacillated between Testudo and Stylemys This: procedure indicates that he recog- 
nized ne close relationships between the species with which he was dealing, S. Be ene 
and the species of Testudo. Professor Cope recognized the validity of fhe genus. While 
regarding the Emydide and the Testudinidz as forming distinct families, he referred Stylemys 
to the former, doubtless supposing that the digits possest three phalanges each. 
It is the opinion of the present writer that the genus in question belongs to the Testudinide. 
Unfortunately, we are even yet not thoroly acquainted with the dstcolos ey of the species 
of Stylemys. Probably thousands of shells of 8. nebrascensis have been observed, yet we know 
of only one skull that has been found actually associated with its shell, no undisturbed foot 
likewise associated, and no cervical vertebre ‘whatever. In the collection at Princeton Uni- 
versity there is the greater portion of a skull which is here figured as belonging to S. nebras- 
ce bigs: but it did not accompany a shell. In the Carnegie Museum at Pittsburg is a shell of 
S. nebrascensis accompanied by the skull. In the American Museum there are various bones 
_ the internal skeleton about which there need be no doubt. All the indications furnisht by 
these remains point to a close relationship with our living land-tortoises. The skull has the 
structure of that of Gopherus (Xerobates). It seems quite certain that none of the digits 
possest more than two phalanges, but the proof is not complete. The scapula, the coracoid, 
the humerus, the forearm bones, the pelvis, and the bones of the hinder limbs agree with the 
corresponding bones of Testudo and Gopherus. A humerus of S. nebrascensis (fig. 492) shows 
that the radial and ulnar processes of the proximal end are twisted toward each other as in 
T estudo, and in a way entirely different from what we see in the Emydide. The form and 
structure of the shell agree rather with that of T estudo than with that of the Emydidz. It is 
true that in the type species, S. nebrascensis, the neural bones and the costals have not under- 
gone the modifications which characterize those of Testudo; but even here we meet with the 
beginnings of these modifications; and in the John Day species they become unmistakable. 
Here the second neural is octagonal, the third is tetragonal, and the costals have become 
wedge-shaped. A peculiarity of the hinder region of the carapace, seen rarely in the Emydide, 
25 
