330 THE AMERICAN NATURALIST. [VOL XXXII, 
cone, respectively, the last being much the smallest, and there 
are two irregular intermediate cusps which represent the 
conules. 
These characters are fairly well seen in the species D. ¢etra- 
gonus, discovered in 1884, the type being a small skull about 
three inches in length. In Seeley’s language (1895, 3) the 
general effect of this cuspidate structure is that there is a sharp 
cuspidate girdle surrounding the subquadrate or subovate crown, 
with one cusp strongly developed on the outer margin, and two 
strongly developed on the inner margin. He found no remains 
of incisor teeth in this specimen, although they may have been 
present. Probably associated with this type were two small 
canines; the reference of these teeth, however, is doubtful. 
There may have been three small teeth in the position of 
premolars and seven in the position of molars, although the 
fragments only indicate five. 
There were two isolated molar teeth found at the same time 
(represented in Joc. cit., Pl. LXXXIX, Figs. 6-9), of very small 
size, which Professor Seeley doubtfully proposed as the type of 
the distinct species D. brachytiara. These teeth are extraordi- 
narily similar to those of Microlestes of the Rhætic of Germany, 
hitherto regarded as a typical multituberculate related to the 
Plagiaulacide. 
It is the species D. mastacus, however (oc. cit; Pl. LX XXIX, 
Figs. 11, 12), which presents the significant resemblance to the 
tritubercular pattern in its molar teeth above mentioned. In 
fact, while not specifically mentioning these strong tritubercular 
resemblances, Seeley observes (1895, 3, p. 1037): “ There is 
nothing with which these teeth can be compared, except the 
molars of some of the higher groups of mammals.” The teeth, 
however, have but one root and belong to skulls which are 
undoubtedly theriodont. 
n the species D. Browni the crown is of a still simpler 
tubercular pattern, with one large internal and evidences of two 
external cusps. : 
