13 
robust, and the external columns are prominent; the intervening spaces 
are impressed, and have a distinct median ridge. Enamel smooth or 
slightly rugose at base of crown. 
Measurcinents. M. 
Length of two superior molars.........020..eeee eee ee 030 
Diameter of first superior molar antero-posterior. ..... .015 
l transverse.......... . 017 
These dimensions are those of the A. cquiceps. 
ANCHITHERIUM LONGICRISTIS, sp. DOV. Z 
This is a smaller species than the two above described, having the di- 
mensions of the 1. bairdi. The best specimen representing it consists of 
a right maxillary bone, which supports all the molars excepting the last. 
The infraorbital foramen issues above the third premolar. The first pre- 
molar is two-rooted ; the second ig not clongate, and is equal to the other 
premolars, or the penultimate true molar, in antero-posterior diameter. 
There are no interior basal tubercles or cingula, but the anterior cingulum 
has a tubercle which is appressed closely to the anterior median. The 
posterior cingulum expands into a large tribedral posterior marginal tuber- 
cle. The anterior median tubercle-crest, appears in the worn state to be 
moderately distinct from the internal ; both it and the posterior middle are 
characterized by their production outwards ; the latter passing between the 
éxterior crescents and forming a junction with their common connection. 
The external cingula are not strongly marked, nor the external faces of 
the crescents impressed ; the latter are convex, and with the median ridge 
little distinct. Enamel smooth. 
Measurements. M. 
Length of anterior six molars........ Perey re Sain acniateunis 062 
" premolarSeriesin. = noua stead sees ttivgawene gO44 
antero-posterior........ .018 
transverse........ saxew O14 
antero-posterior. ..... «- 0125 
transverse............. .0165 
In the Annual Report of the. U. 8. Geol. Surv. Terrs. for 1873,* I gave 
the comparative characters of the three species of this genus then known 
to me, viz.: A. bairdd Leidy ; A. cuncatum Cope, and A. exoletwm Cope. 
TI now give a table in which the three species above described are intro- 
dneed, with the A. condoni Leidy. 
Diameter of second premolar { 
Diameter of second true molar { 
A A tubercle between the internal lobes of the superior molars. 
Larger ; median tubercles well separated ; Jarge anterior and posterior 
mareinal tubercles, sescesasssagetese weceveeas dear viens A. equiceps. 
Smaller; median tubercles not separated ; 10 anterior marginal and a small 
posterior marginal tubercle. .............050- SaROE cee GGue A. bairdi. 
Ad No tubercle between inner lobes. 
* Page 496. 
