FOSSIL VERTEBRATES — REPTILIA 627 
Lycosaurus was a larger form, with a skull nearly eight inches 
long. The upper jaw was very convex on the alveolar border, 
and the lower jaw was correspondingly concave. The whole 
skull was much depressed. 
Cynognathus.— This genus is in some respects the most nearly 
related of the Cynodontia to the Pelycosauria, and in others most 
closely to the succeeding group, the Gomphodontia. The general 
aspect of the skull is that of the Pelycosauria. The cranial region 
is abruptly terminated; the jaws are curved on the alveolar bor- 
der, and the teeth are divided into the separate regions. There 
is, however, only a single temporal arch that is almost certainly 
made up of the two primitive arches combined. The teeth are 
cuspidate, with a single tubercle in front and another behind. 
These are developed on the sides of the tooth as well as on the 
front and rear giving the first appearance of the tubercular type 
of the teeth. The palate bones also present a step in advance of 
the reptilian form. They are extended and unite in the ‘median 
line, thus forming a separate cavity for the nasal organs. This, 
however, does not extend very far back, ending at about the 
middle portion of the roof of the mouth. The occipital con- 
dyle is almost double, the two sides being greatly developed at 
the expense of the median portion. The whole skull of one of 
the best known species was about fifteen inches long. The ver- 
tebrae, pelvis, and limb bones all show the same characters as the 
preceding group. 
Gomphodontia.—The suborder is thus described by Seeley: 
“The Gomphodontia comprises animals with a Theriodont type of 
dentition, in which the molar teeth are expanded transversely, 
and have more or less tuberculate crowns of the type shown in 
Diademodon. The superior and inferior teeth are opposed to 
each other, and the crowns become worn with use, as in the 
Ungulate and other Mammals, and as in the Iguanodont rep- 
tiles. The canine teeth of the upper jaw appear to be worn at 
the extremities. 
“Tt (the skull) appears to show mammalian proportions and 
aspect, in the definition of the large temporal vacuities, by a 
