Thus the carapace is thin. Besides being smaller than the T. guttatu?, 

 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 emasculate ; eight may be counted in 

 M. .01. Width of a marginal costal, .02; thickness on suture, .0055. 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 T. concentrica, on Cottonwood Creek, Wyoming. 

 Axestxjs eyssimus. Cope. 

 Genus et species novae Trionyxchidarum. 

 This genus is represented by a species which is allied to Trionyx, 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 

 vertebras are proccelian, furnished with stout diapophyses and not very 

 elongate ; ball depressed, undivided. The cervical vertebras 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 humeres 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 

 (?) post-abdominal has the free margins acute and serrulate. There is an 

 (?) 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 068 



Diameter at middle , 020 



" end 035 



" caudal do. at ball ,010 



Length " " 023 



" of an ungueal phalange 043 



Proximal depth do. .013 



Length post-abdominal (broken) .... .180 



Width do 120 



Locality of the last. 



