MUSEUM OF COMPARATIVE ZOOLOGY. 169 
Upper Teeth. 
Antero-posterior diameter of molar-premolar series (pm. .065, m. .160), 1225 
Medsurement of the eanines, outside . 3. . 2. cs of dO 
bs e e GORGE ge nS 2 3g ee ee ees Lee 
Diameter of first molar, antero-posterior .047 ; fone Baa ee, 6h te eS 
c third molar, L060) esc Mcmea 7 UO 
at fourth premolar, “ 020 ~'4 = evens ost vets. eee 
$6 canine, oa 35 Stor Ma BL) Mi palatial (27 
Lower Jaw. 
Length of symphysis, . .. tie. BAW eee a om eee aan, WaledlD 
BresdbH Of jaw OpPPOsite CANINES «eye... ses. 6 wesw 2 woees .» O75 
Draapenia Peat tHe CANINES 4. 50.6 5 cs on wie ys ote ee LODO 
epi ot jaw below:tirst molar, 6). ns ee et = ewes 3 --1096 
Antero-posterior diameter of molar-premolar series . . . . . . . .210 
Measurement outside of the canmes . . ... . . . -. «+s. . 060 
Mransverse diameter of te canies , . , sien: *, = 3 - - « ~ 030 
Antero-posterior diameter of the canines . .~ . . . . «...- - 037 
RHINOCERID4E. 
Aceratherium (Rhinoceros) occidentale, Leidy. This species is abun- 
dantly represented in the collection by skulls, teeth, and portions of the skele- 
ton. Little more than the skull has been described as yet, but it is now 
possible to give.a nearly complete account of the osteology of this species, as 
will be done in the final paper. The American species of Aceratherium are 
lighter, more slender, and retain more evidence of lophiodont ancestry than 
the European species, or any of the recent forms. The scaphoid does not 
cover the magnum so extensively as, and the lunar has a greater contact with 
the magnum than, in any of the modern genera, nor does the lunar rest so 
completely upon the unciform as in the latter. The metacarpals are heavier 
than in Hyrachyus, more slender than in the recent types; there were plainly 
four digits in the manus. The phalanges have about the same proportions as 
in the Sumatran rhinoceros. In the hind foot, compared with that of living 
species, we find that the tarsus is higher and narrower, the astragalus more 
deeply grooved, with longer neck and smaller cuboidal facet ; the caleaneum is 
not so heavy ; the metatarsals, especially the lateral ones, more slender. 
In the limb bones the processes for muscular attachment, such as the deltoid 
hook of the humerus and third trochanter of the femur, are much less mas- 
sively developed than in recent species. 
HYRACODONTIDA. 
Hyracodon nebrascense, Leidy. This species is very abundantly repre- 
sented. Its osteology has already been partially described in another place,* 
* E. M. Bull., No. 3, p. 17. 
