118 KANSAS UNIVERSITY QUARTERLY. 
two more than in this species. In No. 179, the mandibular teeth 
correspond in number with X. ¢dawmas, but as the exact number of 
maxillary teeth is not given by Cope in his description of this form, 
the agreement in number of teeth on these parts can not be deter- 
mined. No. 1 corresponds with X. molossus in number of mandi- 
bular teeth, but as the number of maxillary teeth of this specimen 
is somewhat in doubt, the agreement of these parts is uncertain. 
Three more or less constant characters are observed in the arrange- 
ment of the teeth in all the specimens under examination, viz: the 
four small anterior teeth on the maxillary, the two large teeth on the 
premaxillary, the two large anterior teeth on the mandible. The last 
of these seems to be the most constant of the three. The next in 
variation is the number of teeth on the premaxillary, and the one 
of greatest variation is the number of small anterior maxillary teeth. 
From the above it will be seen that the size and arrangement of 
the teeth on the maxillary and mandible cannot be taken as specific 
in either species. The premaxillary teeth show diversity of char- 
acter in size and arrangement quite as marked as the maxillaries 
and mandibles. In some instances the teeth are about equal in 
size, in others there is a noticeable difference, as in No. 301, where 
the posterior 1s very much smaller than the anterior, and in 88, 
where the opposite is the case. 
Some of the specimens possess three premaxillary teeth. In 
No. 266 the anterior is very small and the two posterior large, in 
No. 279 there are three of about equal size, and in 155* four, the 
two anterior of which are large and the two posterior very small. 
Below is given a table showing the great variety in size of the 
specimens: 
MANDIBLE MAXILLARY. 
No . Length of = Depth at Bix Length from Depth an 
alveolar border. coronoid. premaxillary. condyle. 
i 242.5 TASC ates gts sae a niente 102 
Zs 25 et 144 260-+- ELA 
35 279 140 314 119g 
4, 194 10g BEBO 5 78 
88, 260 136 27325 g2 
D5 at oy Les are tones seas Mi As | a esate ect) a has. 4 tae 88.5 
ee op 264 98 
035) TOUS y pteiet TA Meee ses! Sra Lue 3 
155, 215 5 ie 205+ 83.5 
179, 185 94 183 68 
BDO; Wrote, Wis Parcs Me tole em Econ e WhpntC aiapes 84 
2755s 4) Me oreee 220+ 94 
279, ae 263 go 
287), 210 Seale eke 220 80 
301, Dita Lanne Mh ara go 
S14, 242 130 Nene Bait 
353: 195 115 219-- 75 
*It would be well to mention in this connection thut No. 155 possesses ¢haructers 
other than number, size, and arrangement of the teeth. that separate it from 
X. molossus or X. thaumas, the most iniportant of which are the articulation of the 
maxillary and pre-maxillary, the difference in form of the palatine condyle. and the 
greater depth of the dentary with reference to its length. It probably represents 
X, lestero, although this fact I have not yet definitely determined. 
