(From the American Naturalist, October, 1881.) 
GEOLOGY AND PALAIONTOLOGY. 
MAMMALIA OF THE Lowest EoceNr,—Attention has already 
been directed, in these pages to the fauna of an early Tertiary 
period, probably the Puerco formation, which lies below the 
Wasatch, in New Mexico. I have recorded the presence of the 
Creodont genera Periptychus, Triisodon and Deltatherium, and 
probably the Saurian Champsosaurus. I now add the genera 
Lyracotherium, Meniscotherium and Mesonyx, and a number of - 
new forms of considerable interest. These are a new genus allied 
to Esthonyx, and a series of genera and species with a suilline 
type of dentition, but whose affinities are by no means certain. 
This point cannot be determined until the characters of the feet 
are known, 
Conoryctes comma, gen. et sp. nov. Char. gen—Allied to Esth- 
onyx. Inferior canines not rodent-like, with conic crowns. Mo- 
lars 3-3, the first one-rooted, the second two-rooted, the third — 
with an anterior conic cusp and a posterior grinding heel. True 
molars consisting of two lobes, of subcylindric section, separated 
by deep vertical grooves. Enamel developed on internal and 
external faces of crowns. Char. specif—Founded on a mandibu- 
lar ramus which lacks the last molar, and has the crowns of the 
others worn. The external faces of the molars are much more 
exposed than the internal, and are somewhat cuntracted inwards. 
In the unworn crown there is a distinct anterior inner cusp, 
which is soon confounded on attrition. The heel of the last pre- 
molar has a crescentic section, the internal horn the narrower. 
The anterior lobe is a robust cone. The base of the second 
(third) premolar is oblique to the axis of the ramus outwards and 
forwards. It is possible that there is a minute first premolar fill- 
ing the short space between the second and the canine. No cin- 
gula; enamel obscurely plicate; ramus robust. Length of molars 
minus the last, .0465; length of base of first true molar, .o10; 
width of do., .009; elevation of crown do., .0055 ; length of base 
of fourth premolar, .011; width of do., 008; elevation of crown 
of do., .006s. Anteroposterior diameter of base of crown of 
canine, .o19. Depth of ramus at first true molar, .023 ; width of 
do. at do., .013. This genus differs from Esthonyx in the form of 
the fourth premolar. In the latter the anterior lobe is com- 
pressed and trenchant. The species is longer than any of that 
genus, and nearly equal to the Ectoganus gliriformis. 
Catathleus rhabdodon, gen. et sp. nov. Char gen.—With this 
genus I commence descriptions of some genera with bunodont 
dentition, which has some resemblance to that of some of the 
hogs. The one above named, with Mioclenus, remind one of 
1 April and August, 1881. 
