CRYPTODIRA. Ver 
also by the basioccipital. The three elements are usually distinct 
in the occipital condyle. 
The outer border of the tympanic cavity is never completely 
encircled by bone, at least a wide notch being present in the tym- 
panic frame of such forms (the Chelydride, Platysternide, and land 
Tortoises) as have the outer ear-chamber closed behind; in other 
forms, especially the marine Turtles, the stapes are completely, or 
nearly completely, exposed behind. In the Chelonide, Chelydride, 
Dermatemydid, Cinosternidie, and Platysternide the tympanic 
frame is not formed by the quadrate alone, as in the Testudinidee, 
but also by the squamosal and the quadrato-jugal. 
The palatal surface is characterized by the comparative narrow- 
ness of the pterygoids, the outer borders of which are concavely 
arched or convergent behind a more or less distinct process which 
apparently answers to the ectopterygoid process of the Rhyncho- 
cephalia and Lacertilia; this character is most marked in Macro- 
clemmys. least in the land Tortoises. In the latter the palate is 
deeply concave, and the vomer develops a more or less strong 
median keel or ridge which, in Testudo polyphemus and calcarata, 
is produced far back between the pterygoids. A foramen, analogous 
to the palato-pterygoid, is present in all forms save the Chelonide. 
The basisphenoid is separated from the quadrate by the pterygoids, 
which form a suture with the basioccipital, or very nearly reach the 
latter bone, and are in contact with the maxillaries (except in the 
Chelonide); the vomer, which is single, forms a septum between 
the choanze, and joins the premaxillaries on the palate, separating 
the maxillaries (except in some specimens of V’halassochelys). 
The mandible contains a single dentary and five paired elements, 
viz. the coronoid, the opercular, and the angular on the inner side, 
the supraangular on the outer side, and, between the opercular and 
the supraangular, the articular, which is small and with a concave 
surface. 
Hyor Arcu.—The body is short, ossified in one, three, or 
four parts in the freshwater forms; entirely cartilaginous or with 
two or four small ossifications in the terrestrial and marine. The 
entoglossal, which is situated below the anterior extremity of the 
body of the hyoid, is small and cartilaginous. In most freshwater 
Cryptodira three pairs of cornua are present—the anterior very 
small and cartilaginous, the median largest, bony, and with a carti- 
laginous epiphysis, the posterior similar to the median but shorter ; 
in the Chelonide there are likewise three pairs of cornua, but the 
posterior are cartilaginous; in the land lortoises and in Mcoria 
there are no distinct anterior cornua, and the posterior are but 
cartilaginous. 
PecroraL Arcu AND Fore Limsp.—Of the three branches which 
constitute the pectoral arch, viz. the scapula, the precoracoid, and 
the coracoid, the latter is the longest in the Chelonida, the former 
in all other Cryptodira. In the land Tortoises the coracoid is much 
expanded, subtriangular, its width nearly equalling its length. ‘The 
c 
