1054 



CLASS REPTILIA. 



to be absent. An interclavicle, clavicles, and precoracoids are pres- 

 ent, and a sternum was probably always developed. The scapula 

 (fig. 978 bis) has an acromial process with which the precoracoid 

 articulates. The humerus (figs. 978, 982), is characterised by its 

 well-developed distal condyles, and the invariable presence of an 

 entepicondylar foramen ; while its delto-pectoral crest is generally 

 much developed. In the pelvis the pubis is placed entirely in 



advance of the ischium, to which it is 

 completely united, with the presence in 

 some forms of a small fontanelle repre- 

 senting the obturator foramen. The 

 ilium may have almost its whole body 

 in advance of the acetabulum. The 

 tarsus has one centrale ; and the phal- 

 angeals of the manus and pes are typi- 

 cally 2, 3, 3, 3, 3 in number, as in 



Mammals, 



foot 

 type. 



being 



the whole structure of the 

 likewise of a Mammalian 



This order appears to be confined to 

 the Permian and Trias. It has been 

 considered that the Anomodonts are 

 the parent stock not only of all other 

 Reptiles (with the possible exception of 

 the Ichthyopterygia), but also of all 

 Mammals. Later researches do not, 

 however, altogether countenance this 

 view, although there can be no doubt 

 that they are closely allied to the 

 parent stock of Mammals. Recent 

 observations have indeed shown pretty 

 conclusively that this order is directly 

 descended from the Labyrinthodont 

 Amphibians, and more especially from 

 Thus in the small size or absence of the 

 obturator foramen in the pelvis the entire order shows most decided 

 affinities to that group ; while in the small size of the coracoid of 

 some forms, in the presence of a distinct precoracoid (epicoracoid), 

 of very distinct condyles to the humerus, of the centrale in the 

 tarsus, and also in the number of phalangeals, it has characters 

 common both to the Labyrinthodonts and the Monotremes, which 

 are not found together in any other group of Reptiles. These 

 three groups also resemble one another in the non-development, 

 as a general rule, of abdominal ribs ; while signs of affinity be- 

 tween them are shown by the shortness of the tail, and the large 



Fig. 978 bis. — Lateral aspect of 

 the cartilage bones of the right side 

 of the pectoral girdle of a Dicyno- 

 dont ; from the Karoo system of 

 Africa, sc, Scapula ; a, Acromial 

 process of do. ; p.cor, Precoracoid ; 

 cor, coracoid ; gl, Glenoid cavity. 

 Half natural size. 



the Archegosaurian family. 



