240 TRIONYCHOIDEA. 
The foramen magnum is deeper than broad and bordered by the 
basioccipital, the exoccipitals, and the supraoccipital. 
The lower jaw resembles that of the Cryptodira in the number 
of distinct elements, but differs from these as well as all other Chelo- 
nians in the great development of the coronoid process and the 
presence of a strong posterior process formed by the angular, the 
supra-angular, and the articular. 
Hyor Arcu.—The hyoid apparatus is larger in proportion than 
in any other Chelonian. The body, which is concave, is formed of 
three pairs of bones in most genera, of four in Chitra and Pelochelys. 
Two pairs of large bony cornua are present, the hinder attached to 
the last pair of copul, and terminating in a series of from two to 
five additional ossifications. The entoglossal is a rhomboidal car- 
tilage. 
Prcroran Arce anp Fore Liws.—The coracoid is longer than 
either the pracoracoid or the scapula, more or less dilated, and 
with convexly curved outer border. The humerus is strongly 
curved, as in the Chelydridz and Testudinide ; the forearm, on the 
other hand, resembles more that of the Chelonide, the radius being 
considerably longer than the ulna and placed partly below the latter. 
The nine carpal bones are distinct, and there is, in addition, a 
moderately large pisiform. The metacarpal and phalanges are very 
stout in the first finger, and decrease gradually in strength and 
increase in length to the fourth, which is the longest. The phalanges 
number 2.3.3.4.3 in TZrionyx generally and in Pelochelys ; 
2.3.3.5.4in Trionyx triungquis, Cycloderma, Emyda, andCyclan- 
orbis; 2.3.3.6.4 in Chitra. 
Petvis AND Hryp Lims.—The pelvis resembles that of the Chely- 
dride, enclosing a large undivided foramen between the pubes and 
ischia, but differs in the considerably larger pubes, the inner and 
especially the outer process of which expand into very broad wings. 
The ilia are attached to the sacral ribs. 
The tarsus contains six bones (including that which is regarded 
by many anatomists as the fifth metatarsal), viz. one in the proximal 
row, in contact with the tibia and the fibula, and five in the distal. 
The phalanges number 2.3.3.4.2 in Trionyx, Pelochelys, Emyda, 
and Cyclanorbis ; 2.3.3.4.3.in Cycloderma ; and 2.3.3.5.3 
in Chitra. 
