CINOSTERNUM. 15 
tion of the sternum shorter than either of the two lobes; axillary and inguinal scutes 
touching each other by a point ; jaws and throat uniform yellowish. 
I have not seen a specimen of this apparently very distinct species. 
5. Cinosternum hirtipes. (Tabb. XII., XIII., XIV., XV.) 
Cinosternum hirtipes, Wagl. Descr. & Ic. Amphib. t. 30; Strauch, Vertheil. Schildkr. p. 101. 
Kinosternum henrici, Leconte, Proc. Ac. N. Sc. Phil. 1859, p. 4; Yarrow in Wheeler’s Report upon 
Expl. and Surv., Rept. p. 583, t. 16. 
Hab. Norva America, New Mexico (Leconte), Arizona (Yarrow). Mexico, Mazatlan 
and Tres Marias Islands (forrer). 
I consider this species to be the southern and more developed form of Cinosternon 
pennsylvanicum, but the shell is broader in young specimens, and generally more convex 
and raised along the vertebral line in old ones. The sternum is emarginate behind, the 
joint of the hind lobe forming a somewhat curved line. The fixed part of the sternum 
is always somewhat shorter than either the front or the hind lobes; gular plate not 
much shorter than the median suture of the front lobe. The development of the 
axillary and inguinal plates is subject to variation in this species; in a half-grown 
specimen from Mazatlan these two scutes are broadly in contact with each other, 
whilst they barely touch each other in full-grown examples; so it is also in a young 
specimen from Tres Marias Islands, an adult individual from this last locality having 
a merely rudimental axillary plate, which is separate from the inguinal. 
The vertebral keel is very indistinct, even in young examples, the vertebral region 
of the shell being flattened, but never concave as in Cinosternum pennsylvanicum. ‘The 
first vertebral is as broad as long, in old examples bell-shaped, the lateral margins 
being concave. Upper parts of the head brownish or blackish, with irregular yellowish 
spots; sides of the head, jaws, and throat yellow, marbled and streaked with black. 
The tail is very strong and long in the male, and armed with a curved claw; in the 
female it is much shorter and clawless. 
Of this species I have examined five specimens—three (male, female, and half-grown) 
from Mazatlan, and two (female and young) from Tres Marias Islands. The variation 
of form of the shell is well represented in this series. The shell of the largest male is 
64 inches long, the females being 4 inch shorter. The specimens named C. henrict 
were collected in New Mexico and Arizona, and prove the close affinity of the Mexican 
form to C. pennsylvanicum. 
To show the great variation of form to which some species of this genus may be 
subject, three views of each are given of an adult male and female from Mazatlan, and. 
of an adult female from Tres Marias Islands, together with the arrangement of the 
axillary and inguinal plates in a half-grown specimen from Mazatlan. 
