TESTUDINIDA. 431 
from the free border to the notch being only 83 mm. The thickness of the border which articu- 
lated with the eleventh peripheral is 30 mm. The exterior surface of the bone is rather strongly 
convex both from side to side and from above downward. ‘The inferior surface is concave 
from side to side, convex from above downward. The free border is acute. In fig. 564 the 
inferior or inner surface is that toward the left hand. 
The portion of the posterior suprapygal remaining indicates that the width of this bone 
was about 60 mm. It is 20 mm. thick. 
The eleventh peripheral (figs. 563, 565) is narrow above, widening below. The height is 
98 mm.; the width of the upper border, 45 mm.; that of the free border, 87 mm. The exterior 
surface next the pygal is nearly plane; that near the tenth peripheral strongly concave up and 
down, the free border here being considerably flared upward. Fig. 5651 is a view of the end of 
the bone which joined the tenth ‘peripheral. The greatest thickness is 31mm. About 37 mm. 
below the upper border of the bone the thickness 1s mather suddenly reduced. forming a shoulder 
on the inner side of the bone. The upper border is only 13 mm. thick. 
It is necessary to compare these bones with the corresponding ones of various other species 
of Testudo. 
They resemble most the pygal and the eleventh peripheral of 7. rmpensa. ‘The dimen- 
sions of the pygal of the latter species are as follows: Height, 145 mm.; width above, 146 mm., 
width along the free border, go mm. It will be seen fiat. relatively to the height, the width is 
greater. The exterior surface, too, is less convex in all directions. The elev Sieh peripheral of 
T. impensa measures as follows: Height, 122 mm.; width above, 80 mm.; at the free border, 
123 mm. 
T. osborniana, type, has the pygal 110 mm. high; 113 mm. wide above; 80 mm. wide on 
free border. It will be observed that the lower border is relatively considerably wider. The 
outer surface is likewise considerably less convex than that of T. arenivaga. The eleventh 
peripheral of 7. osborniana has a height of 105 mm.; a width of 66 mm. along the upper 
border; and a width of 106 mm. alone: the free border. The two bones have fiereore quite 
different proportions. 
The pygal of 7. pansa is of a different form, being wider below than above, and not so high 
as wide. 
T. undata has the hinder peripherals more strongly flared upward than are those of the 
present species. According to Cope the pygal, too, is fared upward toward the free edge. 
Especially is it to be a teaica with 7. ede of the same beds. The type of the latter is a 
much smaller individual. The table presents measurements of parts common to the two species. 
Measurements taken. Hest ag Destudo 
ede. arentvaga. 
Height of pygal to lower border of suprapygal. : 45 83 
Width of upper border of pygal ; 70 102 
Width of lower border of pygal 43 58 
Greatest thickness of pygal.. . 15 30 
Height of eleventh peripheral . 45 98 
Width of upper border of eleventh peripheral 12 45 
Width of free border of eleventh peripheral 2 87 
It will be observed that the width of the pygal of ZT. arenrvaga is less compared with the 
height than in the case of J. ede. Again, the eleventh peripheral of 7. arenivaga is consid- 
erably broader in comparison with fhe pygal than is the case with these bones in T. eda. 
The differences in the proportions of the bones of the two species is well brought out by 
making plots with the measurements given, those of 7. aren:vaga being divided by 2 
Testudo impensa sp. nov. 
Plates 76, 77; text-figs. 566-571. 
The dry-land tortoise to which the above name has been given was discovered by Mr. 
Albert Thomson, of the American Museum of Natural History, i in 1902, in the Loup Fork 
Miocene deposits of Montana, a short distance above the mouth of the Madison River. The 
locality isin Broadwater County. The number of the specimen is 5867. The parts represented 
