462 [Aug. 15, 
Cope.] 
The carapace is thin, Besides being smaller than the 7. gutiatus, 
Leidy, this species differs in its longitudinal ribs. 
TRIONYX THOMASII. Cope. 
This tortoise is again distinguished from all those known by its sculp- 
ture, this being very delicate and obscure when compared with the thick- 
ness of the carapace. It consists of small tubercles of more or less elon- 
gate form, which may or may not inosculate ; eight may be counted in 
M. .01. Width of a marginal costal, .02; thickness on suture, .0050. So 
in T. concentrica. The costals have very little curvature. The faintness 
of the ornamentation is a marked character. 
Dedicated to my former teacher, Joseph Thomas, M. D., author of Lip- 
pincott’s Biographical Gazetteer, the Pronouncing Gazetteer of the 
World, Baldwin’s Gazetteer, and other important works. 
Found with the Z. concentrica, on Cottonwood Creek, Wyoming. 
AXESTUS BYSsINUS. Cope 
tenus et species nove Trionychidarum. 
This genus is represented by a species which is allied to Zrionyz, but 
which differs in some important respects. The sternal bones are pro- 
vided with an enamel stratum exterior to the usual dense layer of the 
bone, which is not sculptured. The post-abdominal bone has no sutural 
connections, but sends out tooth-like processes at its angles. The caudal 
vertebre are procolian, furnished with stout diapophyses and not very 
elongate ; ball depressed, undivided. The cervical vertebree are elongate 
and relatively very large. The claws are very large, and one at least flat 
and straight; the phalanges have broad trochlear surfaces, which indi- 
cate a moderate amount only of vertical movement. Both humerus and 
femur are curved and with extensive trochanters. The procoracoid and 
scapula are of equal lengths and the coracoid is much dilated distally. 
Char. specif. The portions of plastron preserved are thin for the size 
of the animal, and all the bones are especially dense and smooth. The 
(2) post-abdominal has the free margins acute and serrulate. There is an 
(2) external gently convex edge with a long process extending backwards; 
and one long narrow one inwards. The enamel is white and is marked 
with decussating lines of osseous deposit, as in woven linen. This is not 
the result of wearing. The cervical vertebra is without spine ; it is com- 
pressed in the middle and is without any pneumatic foramen. 
M. 
Length cervical vertebra....... PEP e eRe ees .068 
Diameter at middle 020 
es ME OHCs .085 
e paul dG. ab Wall ee ieee ee ee ee ee os O10 
Length oe ae 
ue of an ungueal phalange.........-+..++-- PETA 043 
Proximal depth OOp 8 aa ees 0138 
Length post-abdominal (broken).......+++-++.+++++++- 186 
Width do. eerie re aU 
Locality of the last. 
ee 
