ANOMODONTS. 



*55 



vertebrae are slightly cupped at each end throughout the series, and intercentra 

 are present. 



The Anomodonts, or Mammal-Like Reptiles. 



Order Anomodontia. 



The last order of Reptiles, which is entirely extinct and confined to the 

 Triassic and Permian epochs, is of especial interest to the evolutionist as being 

 nearly allied to the ancestral stock from which Mammals have originated, and also 

 equally closely related to certain extinct Amphibians noticed in the sequel, which 

 were themselves evidently not far removed from the type whence sprang both 

 Reptiles and Mammals. It should be observed, however, that these Anomodonts 

 show the nearest relationship to the Egg-laying Mammals, and until we know the 

 true affinity of 

 the latter to the 

 other members 

 of the same class, 

 it is of course 

 impossible to at- 

 tempt to define 

 the genealogy 

 more exactly. 

 The Anomodonts 

 are the only 

 reptiles which 

 agree with the \ 

 Egg- laying 

 Mammals in 

 having three dis- 

 tinct bones on 

 each side of the 

 true shoulder- 

 girdle ; that is 



THE EIGHT SIDE OF THE PELVIS (A) AND SHOULDER-GIRDLE (B) OF AN ANOMODONT. 



il, haunch-bone, or ilium ; is, ischium ; pb, pubis ; of, foramen between ischium and 

 pubis ; sc, blade-bone, or scapula ; p.cor, coracoid ; cor, metacoracoid ; gl, cavity for head 

 of upper arm-bone, or humerus. 



to say, a blade-bone, or scapula, above, and a coracoid and metacoracoid below. 

 Then the pelvis is very mammal-like, not only in that its three elements are 

 united, but likewise in the small size of the vacuity, or foramen (of) between 

 the pubis and ischium. It will also be seen from the two figures here given how 

 close is the resemblance between the pelvis and shoulder-girdle of these reptiles, 

 each having one bone above and two below. Even still more marked is the 

 similarity between the upper arm-bone or humerus of the Anomodonts and that 

 of the Egg-laying Mammals ; each having a perforation on the inner border of 

 the lower end, whereas in those existing reptiles which possess such a perfora- 

 tion (with the exception of the tuatera, where there is one on each side), it is 

 situated on the outer border. As a rule, the Anomodonts further resemble 

 Mammals in the absence of abdominal ribs ; and there are important similarities 

 in the structure of the skull. 



