MUlilDJS— SIGMODONTES— ONYOHOMYS. 



105 



of a maguey, in a nest built of fibres of 'zaiate', containing two little 

 ones." 



This animal, compared with the somewhat smaller and the brighter- 

 colored aztecus, bears much the same relations that the large gray californicus 

 bears to the leucopus ("gambeli"), with which it is associated in California. 



Table XXIX.— Measurements of three (dry) individuals of H. MELANoriiRYS (=? mexicanus, DeS.) from 



Southern Mexico. 



Note. — Since writing the preceding, we bave examined tbree otber specimens from Tebuantepec, 

 which, if the same as the types of melanophri/s, lessen the chances that the latter is different from incxi- 

 eanus. But they differ in many respects from the specimens jnst enumerated, being so very much smaller 

 that we cannot satisfy ourselves of their identity. The tail only exceeds the body in one specimen, and 

 here only by little ; in the others, it is about as long, relatively, as De Saussure gives for mexicanus. That 

 these specimens are not immature is shown by the fact that one of them is a nursing female. In color, 

 they are almost precisely like the foregeiug, but do not show the black ring round the eye, nor the dusky 

 spot at base of the metatarsus. Oue of them is pure white below ; another is graj ish (it looks as if soiled) ; 

 while the third has the faintest possible fulvous tinge all along the under parts. 



Much more material than that now in our possession will be required to determine the limits of 

 variation of this large, gray, leucopus-Yike mouse of Mexico, and fix the species upon secure basis. 



Table XXX. — Measurements of three dried specimens, probably of melanopiirys, Coucs (=? mexicanus, 



DeS.), but much smaller. 



Subgenus ONYCHOMYS, Baird. 



Hypndaus sp. Maximilian, Reise, etc. ii, 1841, 93 (ncc auct.). 

 Mus sp. Aud. & Bacu., Q. N. A. ii, 1851, 327. 



Onychomys, Baird, M. N. A. 1857, 458 (type, Hypudams leucogastcr, Max.). — Coues, Proe. Acad. Nat. Sci. 

 Phila. 1874, 1S-2. 



Chars. — Skull strictly as in He.tpe?w?ni/s, but molars larger, with sharper 

 salient and reentrant angles. External form departing from Hesperomys, aud 



