34 



FOSSIL TURTLES OF NORTH AMERICA. 



mm. on the fourth costal and 6.5 mm. on the fifth. This indicates that these vertebrals were 

 very narrow, probably about 30 mm. 



No. 1 18 1 has a label in Cope's handwriting which indicates that it is a portion of his 

 principal specimen (Vert. Tert. Form. West, p. 134), but only a part of the bones described is 

 present. Among these are portions of both the costals of the first pair. On the inner surface 

 of each is a sutural scar for articulation with the axillary buttress. This is 5 mm. wide and on 

 one of the pieces it is 17 mm. long, while the original length has been still greater. On page 

 143 of his Vertebrata of the Tertiary Formations ot the West, Cope refers to certain bones 

 which he had formerly described as xiphiplastrals and as showing that the pubis had articulated 

 with the plastron. With this lot of bones is a rough drawing made by Cope which represents 

 one of these costals as a part of the plastron. The bone (fig. 384) is, however, without doubt 

 a costal, as Cope himself came to suspect. The outside of this costal shows strong concentric- 

 grooves produced during the growth of the first costal scute. 



With the bones just described is what appears to be one of the hinder neurals. It is 16 

 mm. long, 17 mm. wide, and 7 mm. thick. The outer surface is rather rough. A fragment of 

 the plastron, probably about its center, is 9 mm. thick. The right free border of the hypo- 

 plastron is represented by a fragment 23 mm. long. The edge is subacute. From this the bone 

 thickens rapidly to the inner border of the beveled surface on the upper side, where it is 9.5 

 mm. thick. This surface is 15 mm. wide and is bounded interiorly by a sharp groove. 



3860. 



384. 



Figs. 384-386. Echmatemys testudinea. Costal and plastral bones. 



384. Distal end of right first costal, inner surface. X2. No. 1 181 A. M. N. H. Shows scar for axillary buttress. 



385. Mesial portion of right hyoplastron. Xj. No. 1179 A.M.N.H. 



386. Free border of hypoplastron, with section (a) at articulation with xiphiplastron. Xj. No. 1 179 A.M.N.H. 



No. 1 179 may or may not all belong to the same individual, and the bones are probably 

 another portion of Cope's principal specimen. The right hyoplastron (fig. 385) measures on 

 the midline 46 mm. At the midline and where it joined the hvpoplastrals the thickness is 13 

 mm., and 12 mm. where it joined the entoplastral. The femoro-abdominal sulcus crosses 33 

 mm. behind the entoplastron. The humero-pectoral sulcus can not be distinguisht. A frag- 

 ment of the epiplastron has the free edge rather acute. The beveled surface is 16 mm. wide 

 and has a maximum thickness of 9 mm. Fig. 386 represents the upper surface of the left free 

 border of the hypoplastron and a section at the hypoxiphiplastral suture. The beveled area 

 has a width of about 20 mm. and at the summit the bone is 13 mm. thick. It is limited on the 

 inner side by a sharp groove. The beveled surface shows grooves produced by the scute the 

 femoral. A fragment of the left xiphiplastron shows that this was only 36 mm. long on the 

 midline. There was evidently a posterior notch. At the anterior end of the median suture the 

 thickness of the bone is 8 mm.; posteriorly it thins down to 4 mm. 



No. 1 179 includes likewise the proximal half of a costal, almost certainly the sixth of the 

 left side (plate 45, fig. 17). The upper surface presents an elevation outside of the costo- 

 vertebral sulcus, as in the case of those previously mentioned. Anteriorly this sulcus is removed 

 6 mm. from the neural border, but posteriorly it has receded to a distance of 13 mm. This 

 indicates that the fourth vertebral expanded where the sulcus down the sixth costal departed. 



