VERTEBRATES FROM MIOCENE, PLIOCENE AND PLEISTOCENE. 87 
lum is developed on the anterior and posterior sides, but no shelf 
is seen on the inner or outer sides of the tooth. A light coating of 
cement is seen in the valleys. In addition to the lower cheek teeth 
figured the collection contains a fragment showing a part of the 
outer margin of another lower molar on which, however, is pre¬ 
served no additional distinctive characters. The anteroposterior 
diameter of the lower tooth, No. 5083, is 16 mm. The tooth, as 
indicated by this measurement, is therefore much larger than the 
teeth of a species of Parahippus described and illustrated by Dr. 
O. P. Hay on page 42 of this volume (pi. 8, figs. 1 -2). 
The astragalus is shortened beyond that of Mesohippus, thus 
resembling Achacohippus, Parahippus and other more modern gen¬ 
era. Of the two astragali illustrated the left is from the Griscom 
plantation while the right is from the fuller’s earth mine at Mid¬ 
way. The metacarpal, or metatarsal, the proximal part only of 
which was obtained, is a slender bone, the width of the proximal 
articular surface being only 18 mm. On the posterior side may be 
seen the roughened surface for the articulation of the splint bones. 
The median first phalanx, specimen No. 5083, is of relatively 
strong development, while the lateral phlanges are much reduced. 
The median groove in the proximal end of the first median phalanx 
is shallow, and scarcely reaches to the dorsal surface. On the pal¬ 
mar surface the roughened area for the attachment of the inferior 
sesamoid, ligament is confined to the proximal one-fifth of the bone. 
The distal articular surface is very similar to that of the modern 
horse although it is perhaps less reflexed above and below. The 
second median phalanx, referred provisionally to this species is rel¬ 
atively strong. The measurements of these bones are as follows: 
Astragalus, transverse width 17 mm., greatest length 24 mm., 
median first phalanx, length 30 mm.; median second phalanx, 
length 20 mm. 
MERYCHIPPUS SP. 
PI. 11, fig. 1. 
In 1908 the writer obtained from the fuller’s earth mine at 
Quincy a single lower cheek tooth of Mcrychippus. The specimen 
was secured from a workman who found it while digging with a 
pick in the indurated sand above the fuller’s earth stratum. Fur¬ 
ther evidence of its place in the deposit is afforded by the fact that 
