1910.] J\[annval-likc Characters of Cj/vodontff. 119 



The shoulder girdle of Cijiuxjuatlnis (Seeley, loc. n't., p. 93) realizes all 

 the ancestral mammalian conditions which are indicated in the INIonotremata 

 and embryonic Diprotodont ]\larsupialia. The broadly curved anterior 

 border, derived, Broom suggests (1899, p. 768) from the cleithrum of the 

 Pareiasauria, is clearly homologous with the acromion of marsupials and 

 placentals, and with the anterior border of the scapula in the Monotremes 

 (pp. 152, 157). The rudimentary prespinous fossa is confined to the upper 

 anterior part of the scaj)ula. The glenoid cavity is extended transversely 

 as in iMonotremes, and is partly formed by the large coracoid. The pro- 

 coracoid is pierced by the procoracoid foramen (lost in mammals). The 

 humerus (represented in several of the Gomphodontia) was exceedingly 

 mammalian in type (Seeley, 1895.3, p. 29). It is strictly comparable in all 

 its parts with the typical mammalian humerus. The manus is only partly 

 known: /. c, in Microgoniphodon (Seeley, 1895.3, pi. i, fig. 7) and Mluro- 

 suchus (Broom, 1900.2, pi. x, fig. 7). It apparently resembled the Thero- 

 cephalian type, and thei-efore probably contained all the ancestral mammalian 

 conditions (see p. 442 below). The pes is also only partly known (in Micro- 

 gamphodon, Seeley, 1895.3, pi. i, fig. 6) but seems to conform to the type 

 more fully displayed in Oudenodon, and probably therefore contained the 

 same elements as did the pes of the ancestral mammals (see p. 453 and Fig. 

 28, p. 440). 



The pelvis of Diademodon (Broom, 1905.4, pi. x, fig. 3) shows a decided 

 approach toward the mammalian condition in the following characters: 

 (1) The antero-superior part of the ilium is produced upward and forward, 

 while the posterior angle is slightly reduced, thus foreshadowing the much 

 more advanced conditions in the mammalian ilium. (2) A considerable 

 thyroid ("obturator") fenestra, lying between the pubis and ischium, appears 

 for the first time. (3) The pubis is "very mammal-like in structure." 

 Broom (1907.3, p. 6) infers that it may possibly have borne epipubic car- 

 tilages. 



Skull. — The resemblances in the dentition of the Cynodonts to the 

 mammalian type were noted by Owen and all succeeding writers. The 

 dentition of Ci/nognatkus is heterodont, with incisors, canines, premolars 

 and molars, and the cheek teeth are of the incipiently triconodont mam- 

 malian type. The dentition of Sesamodon (Broom, 1905.3), apparently an 

 ally of the Gomphognathidse is very mammalian, the dental formula being 

 I. |, C. 1, Pm + M. Ij. The cheek teeth had small, transversely expanded 

 well-enameled crowns which were ground down after the fashion of mam- 

 malian teeth. This seems to indicate that the motion of the jaw was not 

 strictly vertical as in Cynognatkus, but that as in the carnivorus Marsupials 

 the posterior end of the jaw moved slightly from side to side (see p. 220). 



