116 Bulletin American Museum of Natural History. [Vol. XXVII, 



1908, p. 143) but in most other characters they stand near to the common 

 stem of the Diapsida and Synapsida (Osborn, 1903; Broom, 190S). 



The next group, the superorder or order Therapsida of Broom (1905.2) 

 inchides a series of four orders or suboi'ders, the lowest of which approaches 

 the Pareiasauria and the Pariotichidie, while the highest approaches the 

 Mammalia. 



Dromasauria. 



This very generalized order recently defined by Broom (1907.1), is so 

 far known only from a single type, Galechirus scJioUzi, found in the Middle 

 Permian of South Africa (Broom, 1909). The genus retains the abdominal 

 riblets which are characteristic of the Microsauria and of the more primitive 

 Diapsida, but which are lost in the typical Therapsida, while the facial region 

 is "not unlike that of Pala'ohatteria, there being no specialized canine." 

 But in the structure of the lower jaw, shoulder girdle, pelvis, limb bones, 

 phalangeal formula etc. the genus approximates the order described below 

 (Broom, 1908, p. 1051). 



Therocephalia. 



As defined by Broom (1903.5, p. 7) this Permian suborder, represented 

 by Mlurosaurus, Icticlosuchus and other genera, stands on a lower plane 

 than the "typical Theriodonts," Cynognathus and Galesaunis, as shown by 

 the retention of the following generalized characters : 



The palate is of the general type retained in the Rhynchocephalia, (Broom, 

 1903.2, 1903. G), while the occipital condyle is single as in the typical reptiles. 

 A pineal foramen is retained (Broom, 1903.4). The lower jaw (Fig. 2, 

 No. 1) has large angular, surangular and articular elements, as in the Droma- 

 sauria. Among their progressive characters, the Therocephalia had already 

 developed the single temporal arch, containing the same elements as in the 

 mammals, but distinguished by being continuous with the frontals back of 

 the orbit. The manus is known in Theriodesmus (Seeley, 1888.2), a genus 

 which Broom (1907.3, p. 3) refers to this order. It had all the characters 

 which might be expected in the manus of the remote ancestors of the 

 mammals (see below, p. 439). The pes is not known. 



The Therocephalia enjoyed a great adaptive radiation, the larger forms, 

 forming the sub-order Dinocephalia of Seeley (1895.1, p. 1014) being as big 

 as a rhinoceros, while the smallest, Scaloposaurus, (Owen, 1876, pi. XVI, 

 Figs. 10-15) had a mole-like skull. The teeth are recurved and caniniform. 



