70 



MR. E. R. ALSTON ON THE ORDER GLIRES. [Jail. 18, 



known genus will therefore legitimately give name to the family 

 Geomyidce, the subfamilies standing as Geomyincn and Heteromyince. 

 Here I am inclined to place, at least provisionally, a family of 

 Rodents which flourished in Europe in the later Eocene and Miocene 

 periods, and of which three genera are known. Each of these was 

 at first ascribed to a distinct family of the Hystricomorpha — namely, 

 Theridomys to the Octodontidce, Archceomys to the ChinchillidcR, 

 and Issiodoromys to the Caviidce. M. Gervais was the first to re- 

 move them entirely from that section, uniting the first two in his 

 tribe T/ieridomins of the family Myoxides (which also included 

 Anomalurus). He placed Issiodoromys in his tribu des Pidetins of 

 the Dipodidce, but with the remark that it might have to be rele- 

 gated to the Theridomins* . That these animals were strictly myo- 

 morphine is clearly shown by the form of their mandibles. Now 

 that Anomalurus has been definitely separated from the Myoxidce, 

 there seems to be nothing to unite these ancient rodents with that 



Fia:. 4. 



Mnndible of Capromys pilorides. 



family ; and, both in their very varied dentition and in what we know 

 of their cranial characters, they appear to me to be very nearly related 

 to the Dipodida — the two former to the true Dipodince, and the last 

 to the Pedetince. Meantime it may be best to allow them to stand 

 as a distinct family under the name of Theridomyidce. 



The last family of the Myomorpha, the Dipodidce, is divisible 

 into three plainly marked subfamilies — Jaculina>, Dipodina; and 

 * Zool. et Paloont, Fran^. (2mo ed.). pp. 31-36. 



