1881.] 489 ee 
rior boundary of the crown. This crest is not divided into parts homolo- 
gous with the intermediate tubercles. The crowns of the M. I and II are 
surrounded by a basal cingulum, which in the M. I develops a tubercle at 
the anterior external angle. No internal or external cingulum on P-m. 
IV. Enamel nearly smooth. 
The ramus of the mandible is rather slender anteriorly. The P-m. IV 
is robust, and the cusp is behind the middle of the base of the crown. The 
heel is short and narrow, and has a raised border, connected with the base 
of the main cusp. The cusps of the second true molar are elevated and 
conic, the anterior external the highest, the others subequal. The base of 
the posterior pair is a little narrower than that of the anterior pair. There 
is no central tubercle as in Catathleus rhabdodon, and no basal cingulum 
on either tooth, 
, Measurements. M. 
Length of three superior molars................ seeeee .0160 
‘ : teroposterior......... 0055 
D ‘ anterop 
ete Sy Oe i transverse....... seeeee .0070 
: aol anteroposterior......... -0052 
sia eters superior ME ; transverse ............. .0060 
Length of inferior molar series.............005¢ seeee. .0610 
es es «* true molar series....... eeeeurs aeccee .0160 
Diameters taferior Pan, Tv § anteroposterior ........ -0060 
transverse............. .0040 
Dismeiere inferior Me. 1 § anteroposterior ..... wee 0050 
transverse, .........60. .0040 
Depth ramus at M. II.............. see solass casigewseen 0000 
A number of minor points will distinguish this species from those in- 
cluded among the Mesodonta, and especially those of Pantolestes, which it 
most resembles. The molar teeth are narrower behind, and the fourth 
premolar is larger. It is Mioclenus sectorius, American Naturalist, Octo- 
ber, 1881, p. 831. 
MiocL[{NUS TURGIDUS, gen. et sp. nov. This genus differs from 
Catathleus in the structure of the inferior premolars, which are without 
internal crest or cusp. The inner lobe of the superior premolars is less 
developed than that genus. In the present species the characters of 
Mioclenus are best seen in the subconical tubercles of the premolars, 
particularly that of the heel of the fourth inferior premolar. In the other 
three species this heel is more of a crest and is connected with the princi- 
pal cusp by a low ridge. The four species may be characterized as 
follows : 
a, Cusps of last premolars conical in both jaws. 
Size medium. Last lower molar disproportionately small; cusps low ; 
two anterior inner distinct ; true molars, .018........... M. turgidus. 
aa, Fourth superior premolar with flattened external and conic inter- 
nal cusp ; inferior unknown. 
