1871.] 87 [Cope. 
Hesprromys, Waterhouse. 
A ramus with first and second molars and incisor, agreeing in details 
of structure, with the group with which our recent //. leucopus is type, 
and of the size of that species, not certainly referable to the latter, 
without further comparison. 
ARVICOLA, Lacep. 
Remains of species of the genus are numerous in all the cave forma. 
tions of the United States which I have examined. Those obtained by 
my friend, C. M. Wheatley, are referable to three sections of the genus, 
one of them the group Pitymys, as defined by Prof. Baird,+ the others 
new; one intermediate between Arvicola and Pitymys, and third an ex- 
aggeration of the peculiarities of the last. They are defined as follows, 
the character of the sub-genus Arvicola being added for comparison. 
Arvicola, Lac. Anterior lower molar triangles 1,35, 1 three lobed ; 
middle lower, 13; middle upper, 1 3. 
A. riparia, Ord.* 
Isodeita, Cope. Anter. inf. molar, 1 3 ; 1 three lobed ; 2d inf. mol. 1 2. 
A. speothen, Cope. 
Pitymys, McMurtrie. Ant. inf. mo]. 121, lobed ; 2d inf. mol. 121. 
A. pinetorum, Lec. A. sigmodus, Cope. A. didelta, Cope. A. tetra- 
delta, Cope. 
Anaptogonia, Cope. Ant. inf. mol. 1 4, 1 several lobed, the triangles 
all connected medially, the posterior nearly enclosed. 
A. hiatidens, Cope. 
The third group is represented by the greatest number of individuals 
and species. 
ARVICOLA SPEOTHEN, Cope. 
Sp. noy. 
This species is represented by the entire dentition of the left ramus 
mandibuli, with a few fragments of the adjaeent bone. As already. 
pointed out, its characters entitle it to rank as a distinct section of the 
genus. Thus the triangles of the inner side of the anterior inferior mo- 
lar are one less than in any species of the section Arvicola. The anterior 
loop presents two well marked angular basal areas, while its terminal 
portion is regularly rounded. The accompanying outline will give a good 
+I have depended on Prof, Baird’s well known work in studying this genus. 
#ARVICOLA RIPARIA, Ord. 
Baird, U. 8. Pac. R. R. Surv , viii, 522. 
This species has not yet been found in the Port Kennedy cave, and I introduce it for the purpose 
of recording its occurrence in the cave breccia, Wythe Co., Virginia, whose contents I examined 
and described in Proc. Am. Phil. Soc,, 1869, 171. Itisrepresented by a left ramus mandibuli, en- 
tire except in the angle and condyle, and with complete dentition, The size and proportions are 
identical with those of the existing species, as are also the triangles and form of terminal trefoil 
lobe of the anterior inferior molars. There is no difference to be observed between the third infe- 
rior molar when compared with that of 4, riparia from Pennsylvania, but the anterior alternate 
triangles of the second, are not isolated, the reentrant inflection of the external enamel plate not 
reaching the internal, as in the recent animal, 
