

m i It 



46 



MONOCIJAIMIS OP NORTH AMEUICAN IIOUKNTIA. 



^ \: 



''Mf 



> Mm 



to Hespcwwys of Baird, as limited l)y tliiit aiiflior, as above cited. Ctilomys, 

 as used l)y Aiidulmii and Ikchinan for their Mus aureolas, is not a synonym, 

 sul)geiicrically, of Cnlomy.^, Waterlioiise ; aureolas being strictly of the same 

 group as leucopuK, while Calomys of Waterhouse refers to the South American 

 elegans, Uimculatus, &c. The only other name, except Hespcromijs, that we 

 can find has been applied to the present subgenus, is Musculus of Rafinesque. 

 Tills name, in strict teciinical conformity with the rules of nomenclature, 

 ought to be adopted ; and it is nothing to the point that its proposer did not 

 jiroperly define it, for we know that he used it in connection with leucopus. 

 ]}ut the name is so inseparably connected with Mas muscalun, that to use it in 

 a different connection, and one where the tribal distinctions from Mas especially 

 rc'-'ire to be signalized, would result in an evil of far more consequence than 

 the breach of a rule of nomenclature. While we regret that we happen to be 

 personally interested in tiiis, one of the rare cases where tiie law of priority 

 must be set aside, nevertheless we cannot disregard its obvious requirements. 

 The following paragraph is diagnostic of tiic subgenus VespcrimuH : — 

 Chars. — Of medium and small size, lithe form, and quick movement. 

 Eyes large, prominent. Snout pointed. Ears large, rounded, thin, finely 

 scant-pilous ; antitragus evident but not valvular. Fore feet hardly or not 

 iialf as li>!ig as the soles ; palms naked ; fore claws not larger than hind claws, 

 that of the -'l)soln^o thumb rather a nail ; other fore digits slender, 3d and 4th 

 subequal and longest, 2d and 5th successively much shorter. Hind feet long, 

 slender; soles 6-tuberculate, naked, or scant-furred on the posterior third ; 

 2d, 3d, and 4th toes much longest and subequal, oth shorter, 1st much shorter. 

 Tail terete, slender, closely hairy, subequal to tlie trunk in length (ranging 

 from as long as body alone to a little longer tlian head and body togctiier). 

 Pelage sof>, close, glossy, with but few longer bristly hairs ; feet and under 

 jiarts white or wliitish ; body and tail more or less distinctly bicolor. No 

 lauuginous tuf\s of hair al)out the ears. Back upper margin of orbit not 

 beaded. 



e skull and teeth of all the North American Hesperomy.i are so mucli 

 f.-...e, while the external form is so different in the three sections of Vesperi- 

 mus, Onychomys, and Oryzomys (as will be evident upon comparing the 

 diagnoses given l)cyond of tliese gencraX tiiat we hav(« preferred to deiine 

 Vt'spcrimus chielly by e.xlernal cluxrarters. The skull of Onychomy.i merely 

 differs from that of Vrsprrimux in being a little larger and heavier, not (luilc 



^r.: 



