4 
Measurements. M. 
Length of alveolar edge of mandible.... ..........0+2. .120 
“- from diastema to canine tooth...............+- .080 
‘of centrum of atlas.......... LaiGiedsd OE OR sore e -010 
se NE se OO ARIS sclatalawiseeate aa ened Lweapa WOOL 
“« _-« centra of following five vertebra.......-..... .O7L 
«« jlium at acetabulum........- asigamste. seeeeee 040 
The Janciform shape of the skull with its consequent peculiarities distin- 
guishes this species from the Clepsydrops natalis, and the Dimetrodon in- 
cisivus. The canine tooth is more posterior, the teeth more ‘numerous, 
and the alveolar borders less curved than in either of those species. The 
diastema is less excavated, and the muzzle less obtuse. 
THEROPLEURA OBTUSIDENS, Sp. nov. 
This species is represented by nearly all parts of the skeleton, including 
jaws of both sides with teeth, numerous vertebree, and bones of the limbs. 
Many of these pieces are preserved in continuous masses, thus greatly aid- 
ing in the identification of parts. « : 
Although the species is not larger than the Theropleura retroversa, the 
neural arches are coéssified with the centrum. a 
The jaws are long and rather slender, and there is no such inequality in 
the sizes of the maxillary teeth as in the genera Dimetrodon and Clepsy- 
drops ; the canine being scarcely larger than the others. The crowns are 
elliptical in section at the base, with straight sides; the sections of the 
crowns are lenticular, and the apices are not very acute. The superficial 
coating is striate with fifteen or sixteen rather obtuse ridges The cutting 
edges are not very acute, nor are they denticulate. The number of teeth 
in the dentary bone cannot be precisely stated, but is about twenty-one. 
The mandibular articular face consists of two open parallel grooves, one 
shorter than the other, extending obliquely to the long axis of the jaw.’ 
The palatal dentigerous bone is quite different from that of Dimetrodon. Its 
inferior face instead of being narrow, is rhombic. The ascending process 
arises from one of the terminal] angles of the rhomb, and the horizontal 
process continues from the opposite angle in line with the inferior surface. 
The borders of the rhomb next to the ascending process are dentigerous ; 
the one bears a single series of four large teeth ; and the adjacent angle and 
side bear numerous small teeth. 
The vertebre have the elongated neural spines of the allied genera, and 
they are simple. The centra have curved articular margins indicating the 
presence of intercentra, which are, however, not preserved. Traces of 
sutural articulation with the neural arch remain. Many of the centra are 
much compressed and have a narrow sharp median keel. Ina few vertebrae, 
apparently from the posterior part of the column, an angular ridge extends 
posteriorly from the base of the diapophysis; this is apparent also on a 
caudal centrum. This point is characteristic of the 7. retroversa, but I do 
not find the large capitular facet of that species in the 7. obtustdens. The 
