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worn on the anterior border, and serrated on the hinder margin, llemnants of canine teeth are indicated which have been replaced by those which persist.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.
BioStor
