No. 2328. PLEISTOCENE VERTEBRATES IN UNITED STATES— HAT. 87 



The left second peripheral (pi. 3, fig. 1) lacks its inner half. The 

 length along the free border is 17 mm. ; the greatest thickness of the 

 bone is 7 mm. The bone is only slightly recurved upward. The right 

 seventh peripheral (pi. 3, fig. 2) is 18 mm. long and 15 mm. high. 

 Its upper and anterior corner is broken off. Seen from within, the 

 anterior part is occupied by a part of the sternal chamber. The 

 interior part presents the buttress which rose to meet the sixth rib. 

 A part of the buttress is split off, but there is left a pit for the distal 

 end of the rib. The edge which articulated with the hypoplastron is 

 thin and sharp, so that the union of the two bones appears to have 

 been weak, at this point at any rate. The right ninth peripheral is 

 intact. It is 14.5 mm. long, 16 mm. high, 5.5 mm. thick in front and 

 a little thinner behind. 



The right first costal plate lacks about the distal half. It is 21 mm. 

 wide. The proximal end is occupied by parts of the first and second 

 vertebral scutes. The other rib fragment by its narrowness appears 

 to indicate the usual alternation of wide and narrow costals. The 

 elements of the hypoplastron appear to have come forward nearly 

 to the hyohypoplastral suture. It is believed that the bone on the 

 right side (left of the figure) reached the suture mentioned. As 

 shown by the figure (pi. 3, fig. 3) there is a fragment of the xi phi- 

 plastron which belonged to the free border, but just how near it 

 approached the remainder of the xiphiplastral is uncertain. The 

 plastron is about 9 mm. thick at the crossing of the hypoxiphiplas- 

 tral suture and the median one ; but it thins rapidly in all directions. 

 The lower surface of the hypoplastron presents ridges and grooves 

 due to the growth of the horny plates. The greater part of the sur- 

 face of the carapace is smooth, but a fragment of one peripheral dis- 

 plays ornamentation. 



Family EQUIDAE. 



EQUUS LEIDYI Hay. 



In the Whitesburg collection there is an upper right second pre- 

 molar of a horse which is referred to this species (U. S. Nat. Mus. 

 No. 8945). It is worn down to about one-half of its original length, 

 and the anterior style is broken off. The height of the crown is 42 

 mm. ; the width across the worn face at the posterior outer style, 25 

 mm. The length of the) grinding surface was probably close to 35 

 mm. When compared with a corresponding tooth of Equus com- 

 ■plicatus., from the region about Charleston, South Carolina, the 

 Whitesburg tooth is seen to be considerably smaller. There is pres- 

 ent also a part of an uncut milk molar of a horse, probably E. Uidyi 

 (Cat. No. 8946). 



