OSSEOUS SYSTEM. 135 



sphenoid upon either side, and supports the parietal bone, which 

 rests upon it like the capital upon a pillar. This' columella corre- 

 sponds acconding to some anatomists with the great wings of the 

 sphenoid. The inferior wings of the sphenoid are very large in 

 the Chelonia, and united with the body of the bond, and to each 

 other in the middle line, by suture ; they represent at the same 

 time the great alae, and unite in front with the palatal bones. In 

 most of the Sauria they are narrow and elongated, frequently sup- 

 port teeth, and are connected by synchondrosis with the body of the 

 sphenoid ; they are separated from each other, and abut posteriorly 

 against the os quadratum, and in front, generally by means of two 

 processes, against the palatal and jugal bones. In the Crocodiles 

 they are very broad, unite in the middle line by suture, and con- 

 ceal the body of the sphenoid. In the Ophidia the two wings are 

 widely separated, very elongated, frequently provided with teeth, 

 and bifurcate into an internal piece united with the palatal bones, 

 and which can be regarded as an internal pterygoid process, and an 

 external corresponding with the external pterygoid, and connected 

 to the superior maxilla. The first piece extends very far back 

 posteriorly to the union of the os quadratum with the inferior 

 maxilla. The last piece is considered by many anatomists as a 

 particular bone under the name of os transversum. The temporal 

 bone is divided upon an average in all three orders into four pieces. 

 In the direction inward and backward is situated the petrous 

 bone, posteriorly and externally the mastoid, which in the Ophidia 

 is very much elongated and style-shaped, but shorter in the other 

 orders ; in front of and in contact with this is generally placed the 

 squamous element, united in the Chelonia and Sauria by suture 

 with the parietal and jugal bone, but being quite free in the 

 Ophidia, and advanced further forward. This piece is however 

 viewed by many anatomists as a peculiar bone, under the name of 

 anterior frontal, and being divided in the Tortoise into two pieces ; 

 the posterior of them has been in like manner termed the posterior 

 frontal. The right interpretation of these bones has, however, given 

 rise to much contrariety of opinion, relative to which the reader 

 must consult and compare the special treatises on the osteology of 

 the Reptilia. The articulating portion of the temporal, called the 

 quadratal or tympanic bone, is particularly broad and concave in 

 the Chelonia so as to be adapted for the reception of the large tym- 

 panic membrane, and superiorly is united by suture with the 

 squamous and mastoid elements, while inferiorly it always projects 



