2 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62 
Genus KINOSTERNON Spix. 
Carapace more or less depressed; marginal shields, one azygos 
nuchal and 11 pairs. Plastron articulating with the marginals by 
suture, front and hind lobe moveable; gular shield single or absent; 
pectoral shields not extending on the bridge. Postorbital and tem- 
poral arches moderate. Digits webbed; fingers all clawed, outer 
two clawless. ‘Tail short. 
KINOSTERNON ARIZONENSE, new species. 
Plates 1 to 5. 
Type.—Male. Cat. No. 10463, U.S.N.M.; consists of the nearly 
complete carapace and plastron, the latter lacking the anterior lobe; 
lower jaws, fragmentary verte- 
= “A Y brae, limb bones, etc. 
oe Neer anaes ay Paratype.—Female. Cat. No. 
Uiimews - \ 10462, U.S.N.M.; consists of the 
“ nearly complete carapace and 
plastron. 
Type-locality.—Benson Local- 
ity Quarry, two miles south of 
Benson, Cochise County, Ari- 
zona. 
Horizon.—Pliocene. 
Collector.—J. W. Gidley, 1921. 
When found the specimens 
were entirely disarticulated and 
broken into numerous pieces, 
and the assembling of these por- 
tions has resulted in some dis- 
tortion and other imperfections 
in the carapace as may be ob- 
served in the illustrations (see 
Fic. 1. CARAPACE OF KINOSTERNON ARIZONENSE. 
No. 10463, U.S.N.M. Type. MALe. C. 1, C. 8, pls. 1 and 3). Some small areas 
COSTAL BONES 1 AND 8; N, 1, 2,3, 4, 5,6, NEURAL of both upper and lower shells 
BONES 1 TO 6; NU, NUCHAL BONE; PER 10, TENTH pie 
PERIPHERAL BONE; PY, PYGAL BONE; sPY,supRA- WETe MISSING, although as a whole 
PYGAL BONE: V1, V5, VERTEBRAL SCUTES 1 AND 5. they are in a remarkably good 
ONE-HALF NATURAL SIZE. : 
state of preservation. 
The much larger size of the fossil forms at once distinguishes them 
from any living species, and I therefore propose the name Kinoster- 
non arizonense for their reception. 
A comp rison of the two specimens show them to be very similar, 
in the extent and arrangement of the various bony elements, as 
well as the epidermal shields which covered the osseous parts in life. 
That the larger specimen is a male appears to be shown by the con- 
cavity of the posterior lobe, the swelling outward of the lateral borders 
of this lobe back of the inguinal notch, and the fact that it fills this 
