1053 



CHAPTER LIII. 



CLASS RE PTI LI A— continued. 



Orders Anomodontia, Sauropterygia, and Chelonia. 



Theromorous Branch. — The Reptiles included in this branch 

 or alliance may, for the present at least, be arranged in a single order, 

 although some writers would prefer to regard the suborders into 

 which this order is here divided as of ordinal importance. The 

 most remarkable features found in this order are the resemblance on 

 the one hand to the Labyrinthodont Amphibia, and on the other to 

 the Monotreme Mammals. 



Order I. Anomodontia. — This order, which is equivalent to the 

 Theromora (Theromorpha) of Professor 

 Cope, presents the following characteristic 

 features. The body is lacertiform, and 

 the limbs are adapted for walking. The 

 skull is comparatively short, with a fixed 

 quadrate, a parietal foramen, either one 

 or two temporal arcades, and large nasals ; 

 in the palate the pterygoids meet together 

 in front of the basisphenoid, which they 

 also join, but diverge anteriorly ; while the 

 palatines are generally small, and placed 

 internally to the pterygoids, as in Mammals. 

 When the temporal arcade consists of only 

 a single chain of bones, it is a squamoso- 

 maxillary one (p. 904). The dentition is 

 thecodont, but the teeth may be anchy- 

 losed to the bone. The vertebrae have 

 amphiccelous and in some cases noto- 

 chordal centra ; the dorsals carrying long 



transverse processes, and the ribs articulating by double heads in 

 the anterior region of the trunk. As a rule abdominal ribs appear 



Fig. 978. — The palmar aspect 

 of the left humerus of Ptychosi- 

 agum Mtirrayi; from the Karoo 

 system of South Africa. Half 

 natural size, a, Entepicondylar 

 foramen with the bridge broken 

 away. (After Huxley.) 



