——— 
PALA ONTOLOGICAL APPENDIX—EXTINCT RODENTIA. 947 
ARVICOLA (ISODELTA) SPEOTHEN Cope. 
Arvicola speothen Corr, Proc. Amer. Phil. Soc. Phila. 1871, 87, fig. 13. 
Described from “ the entire dentition of the left ramus mandibuli, with a few frag- 
ments of the adjacent bone”, from the Port Kennedy bone-cave, Pennsylvania. 
Anterior lower molar with one less triangle “than in any species of the section Arvi- 
cola”, and hence regarded as representing a new subgeneric type. 
ARVICOLA (PITYMYS) TETRADELTA Cope. 
Arvicola tetradelta Copy, Proc. Amer. Phil. Soe Phila. 1871, 83, fig. 14. 
Described from a portion of the skull embracing the second and third upper molars. 
Differs from the other known North American Arvicole in the form of the enamel loops 
of the molars. Port Kennedy bone-caves, Pennsylvania. 
ARVICOLA (PITYMYS) DIDELTA Cope. 
Arvicola didelta Corr, Proc. Amer. Phil. Soc. Phila. 1871, 89, fig. 15, 
Described from “the mandibular rami of five and the superior dentition of proba- 
bly three individuals”, from the Port Kennedy bone-caves. Allied to Arvicola (Pitymys) 
pinetorum. 
ARVICOLA INVOLUTA Cope. 
Arvicola involuta Corr, Proc. Amer. Phil. Soc. Phila. 1871, 89, fig. 16. 
“Established on a nearly complete ramus mandibuli, with the dentition perfectly 
preserved”, from the Port Kennedy bone-caves. It is said to be “nearly allied to the 
A. pinetorum, differing principally in the form of the anterior lower molar”. About the 
size of A. riparius. 
ARVICOLA SIGMODUS Cope. 
Arvicola sigmodus Corr, Proc. Amer. Phil. Soc. Phila. 1871, 90, fig. 17. 
Based on “three imperfect mandibular rami, two with the dentition complete, the 
other with the posterior molar only wanting”. About the size of A. riparius. Its 
characters are said to be near those of ‘A. austera, Lee.” 
ARVICOLA (ANAPTOGONIA) HIATIDENS Cope. 
Arvicola hiatidens Corr, Proc. Amer. Phil. Soc. Phila. 1871, 91, fig. 18. 
Based on several molar teeth, which are several times larger than the correspond- 
ing teeth of any of the above-named species, “and suggest the genus Fiber”. Itis sug- 
gested that it may not be referable to either Arvicola or Fiber, and that it may require 
to stand as a separate genus. From the Port Kennedy bone-caves, Pennsylvania. 
GEOMYID. 
GEOMYS BISULCATUS Marsh. 
Geomys bisulcatus Marsu, Amer. Journ. Sci. and Arts, 3d ser. ii, 171, 121. 
Apparently nearly allied to Geomys bursarius. From Pliocene strata, near Camp 
Thorne, Loup Fork, Northern Nebraska. 
