Miscellaneous. 387 



MISCELLAJ^EOUS. 



JResearclies on the Structure, Oi-ganization, and Classification of the 

 Fossil Heptilia. — Part IX, Section 5. On the Cynodontia. By 

 H. G. Seeley, F.II.S. 



The Cynodontia is a division of the Theriodontia in which there 

 are long and large temporal vacuities in the skull, formed chiefly by 

 the squamosal and malar bones ; in which there is no descending 

 pedicle to the squamosal bone ; in which the occipital condyle is 

 crescentic and imperfectly divided into two lateral parts ; and in 

 which the hinder molar teeth, lai'ger than the incisor teeth, develop 

 anterior and posterior cusps, are compressed from side to side, and 

 overlap with shear-like action the teeth of the mandible. The prin- 

 cipal new genera included in this group are Cynognathus, which is 

 known from several skulls and one fairly complete skeleton, and 

 the genus Tribolodon, which does not differ in a striking way from 

 the small Cynodouts previously known, referred to the genera 

 GuL'saurus, Nythosaurus, and Thrinaxodon. 



The skeleton of Cynognathus crateronotiis was found at Lady Frere, 

 near Queenstown. A single tooth of this genus had alread}- been 

 obtained by Air, Alfred Brown at Aliwal North. The skull is be- 

 tween 15 and 16 inches long, 8 inches high at the orbits, and 

 higher at the occiput, where it was about 9 inches wide. The 

 lateral aspect is remarkably mammalian, owing to the great deve- 

 lopment of the dentar}' bone, which forms a new type of lower jaw, 

 and has a greatly developed coronoid process, and to the form of the 

 zvgoma. On the palate the palatine and transverse bones form a 

 descending arch between the rami of the mandible, as in crocodiles, 

 Sphenodon, and Lizards. The composite structure of the lower jaw 

 is seen on its inner side. The prefrontal and postfrontal bones 

 remain distinct. There is a small quadrate bone embedded in the 

 large squamosal bone. The latter resembles that of mammals, both 

 in its extension along the zj-goma and its expansion as a squamous 

 plate on the side of the brain-case. 



There are four incisors in each premaxillary ; their margins are 

 serrated. There appear to be but three mandibular incisors on each 

 side, so that the type resembles Cynochampsa ; but there is no 

 evidence of close affinity with that genus. The canine teeth are 

 large, worn on the anterior border, and serrated on the hinder 

 margin, llemnants 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. 



