Cope.]} 492 (Sept. 17, 
anterior outer cusp increases in size anteriorly, and is the large cusp of 
the P-m. IV. It sends a branch backwards on the inner side of the crown 
which forms the edge of the narrow concave heel. There are no cingula 
except a short one on the anterior corners of the base of the crown of the 
P-m. IV. Enamel obscurely wrinkled. : 
Measurements. M. 
Length of posterior four molars.......... # sens vice 20180 
Ditmetersiet Pan 1¥ { anteroposterior..... . .0050 
transverse.........--- 0035 
‘ anteroposterior ....... .0050 
eens ; transverse........-.-- 0085 
: anteroposterior........ .0040 
Tiaumpiste a My TT ; transverse......... oe. 0082 
Diameters of M. TIT { anteroposterior....... 0045 
tTANSVEYSC.....2.---- - 0080 
Depth ramus at M.-T...... ce. ecw cece en cece eens ecees .0110 
Thickness!" §" {© esses seis s rouse sie soelesertemsew 50060 
PHENACODUS PUERCENSIS, sp. nov. Three individuals. Last superior 
molar smallest ; first and second true molars with six tubercles, two ex- . 
ternal, two median and two internal. <A strong basal cingulum except on 
inner side. Inferior true molars besides the usual five tubercles, furnished 
with an anterior ledge with a tubercle at its interior extremity. A weak 
external basal cingulum. A little larger than the P. vortmant. Length 
of superior true molars M. .021; length of base of crown of M. II 
006; do. of M.I.008; width of do. .008; length of base of crown of. 
inferior M. III .0085; width of do. in front .006; depth of ramus at M. 
I .019. 
PHENACODUS ZUNIENSIS, sp. nov. The least species of the genus, rep- 
resented by the mandibles of two individuals. The first and second true 
molars are narrowed in front, and there is no distinct anterior ledge, only 
a minute anterior inner tubercle. The external cingulum is more distinct 
and the enamel is wrinkled. The fourth premolar has a short base and 
the inner cusp is much smaller than the principal one; it has a wide heel 
and an anterior basal tubercle. Length of true molars, M. .018; of last 
true molar .006; - of base of first true molar .006; width of do. .004; 
depth of ramus at do. .011. 
PROTOGONIA SUBQUADRATA, gen. et sp. nov. Fourth superior premolar 
with one external and one internal lobe. True molars with two external, 
two internal, und two intermediate lobes, both the latter connected with 
the anterior internal by a ridge. Supposed inferior true molars with two 
Vs with weak anterior branches; last true molar with heel. 
This genus will enter the Chalicotheriide of my system of Perissodac- 
tyla,* if the feet are found to possess the requisite characters. It is 
allied, apparently, also to Hyracothertum, but differs in the Vs of the infe- 
*See Proceedings Amer, Philosoph. Society, 1881, p. 877-8. 
