292 Prof. H. G. Seeley. Researches on the Structure, [June 21, 



of close affinity with that genus. The canine teeth are large, worn on 

 the anterior border, and serrated on the hinder margin. Remnants of 

 canine teeth are indicated which have been replaced by those which 

 persist. There are nine molar teeth, of which the first five are smaller 

 than the posterior teeth. Those teeth are more than half as wide again, 

 from front to back, as the anterior teeth. The hinder teeth have the 

 principal cusp directed backward, with one subordinate pointed cusp 

 on the front margin, and two subordinate cusps on the hinder margin. 

 The crowns of the teeth stand high above the alveolar margin in this 

 species. They are intermediate in form of crown between Canis and 

 Zeuglodon. 



The nares are terminal, divided, lateral, and arch forward in front 

 of the alveolar margin. The orbit of the eye is 8 in. behind the 

 extremity of the snout, nearly circular, and separated from the tem- 

 poral vacuity by the post-frontal bone. The post-frontal bones con- 

 verge backward along the parietal crest. The malar bone develops a 

 slight descending process on its inferior margin. There is no inter- 

 orbital septum ossified. The type species of Cynognathus shows, on 

 the one side preserved, a small post-orbital foramen, comparable to 

 that of Procoloplion, and the author considers that the enlargement of 

 this foramen makes an essential difference in plan between the skulls 

 of Teleosaurs and Theriodonts, and regards the Mammalian zygoma 

 as resulting from the obliteration of the post-orbital vacuity which 

 defines the superior and inferior temporal arcades in Saurischia and 

 other Beptilia. 



In general structure of palate Cynognathus resembles Lycosaurus. 

 There is no transverse boundary to the hard palate, but the palato- 

 nares are lanceolate. The author finds that the downward develop- 

 ment of the bones of the palate at the posterior borders of the nares, 

 while thoroughly reptilian, approximates to the condition in Mam- 

 mals. 



The form of the lower jaw approximates to that of the older 

 Mammals and lower Mammalian types, leading to the conclusion 

 that the Mammalian lower jaw consists essentially of the dentary 

 bone. The dentary bone is compared to that of Microconodon in 

 form, and development of the angle of the jaw. 



The shoulder girdle consists of a large scapula, small coracoid, and 

 compressed pre-coracoid. The scapula demonstrates the origin of a 

 spine like that of the scapula in Mammals, by outward development 

 of the anterior border of the scapula in Reptiles. This spine is de- 

 fined by a pre-scapula development anteriorly. The spine may have 

 been originally a separate ossification, such as in Pareiasaurus has 

 been named epi-clavicle. It terminates in an acrornion which is re- 

 flected forward. 



The humerus is imperfectly preserved, but has the distal con- 



