240 TRIOXYCirorDEA. 



The foramen magnum is deeper than broad and bordered by tbe 

 basioccipital, the exoccipitals, and the supraoccipital. 



The lower iaw resembles that of the Cryijtodira in the number 

 of distinct elements, but differs from these as well as all other Chelo- 

 nians in the great dcveloi)inent of the coronoid process and the 

 presence of a strong posterior process formed by the angular, the 

 supra-angular, and the articuhir. 



IIyoii) Alien. — Tlie 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 Pehiheliis. 

 Two pairs of large bony cornua are present, the hinder attached to 

 the last pair of copnhc, and terminating in a series of from two to 

 five additional ossifications. The entoglossal is a rhomboidal car- 

 tilage. 



Pkctoral Aech and Fore Limb. — The coracoid is longer tlian 

 cither the pnccoracoid or the scajaila, more or less dilated, and 

 with convexly curved outer border. The humerus is strongly 

 curved, as in the Chelydridic and Testudinidae ; the forearm, on the 

 other hand, resembles more that of the Chelonida), the radius being 

 considerably longer than the ulna and placed partly below the latter. 

 The nine carp;il 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 Trlonya; generally and in PclocJult/s ; 

 2 . 3 . 3 . 5 . 4 in Trionyx triunguis, Cycloderma, Emyda, andCyclan- 

 orbis; 2 . 3 . 3 . 6 . 4 in Chifra. 



Pelvis and Hind Limb. — The pelvis resembles that of the Cheh"-- 

 dridae, 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 tbe 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, PelocJielys, Emyda, 

 and Cyclunorhis ; 2. 3. 3. 4. 3. in Cycloderma ; and 2.3.3.5.3 

 in Chitra. 



