1893.] NATURAL SCIENCES OF PHILADELPHIA. 409 



smaller size; b, cinnamon of upper parts; c, cinnamon of sides; d, 

 plumbeous bases of belly hairs; e, outside of foreleg dusky to wrist; 

 /, smaller skull ; g, mastoids projecting behind plane of occiput ; h, 

 audital bullae united by an anterior symphysis ; i, relatively broader 

 interparietal; j, shorter and blunter coronoid process; k, lower pre- 

 molar smaller than last molar. 



(4 ). Having shown that the evidence is against considering lordi, 

 mollipilosus and monticola synonymous and that their closest affinities 

 are not between mollipilosus and lordi, as suggested by Dr. Merriam, 

 but between mollipilosus and monticola, let us consider their relation- 

 ships to Oricetodipus parvus. If Peale's "mouse" can ever be proved 

 to be a Perognathus I should predict, on geographical grounds, that 

 it is more likely to be the same as mollipilosus than any other of 

 the trio. But there is strong evidence in Peale's minute description 

 that Oricetodipus parvus is not a Perognathtis at all, but a suckling 

 Perodipus, or five-toed kangaroo rat. 



This evidence may be briefly summed — a, Dr. Merriam proves it 

 to be, (Amer. Fauna., p. 8), a "very young" animal; see also 

 Baird, (Mam. IS. Amer., p. 425); b, " head and body ecpial;" pro- 

 portions never (?) seen even in half-grown Perognathus but correlated 

 with the proportions of adult Perodipus; c, "whiskers numerous, 

 white, a tuft of white hairs or bristles on the chin ; " this tuft is pre- 

 sent in Perodipus agilis; I do not detect it in Perognathus; d, 

 "fore- legs small, feet moderate, * :;: :;: hind legs long, the feet large 

 and strong, five-toed;" almost the reverse of this obtains in Perog- 

 nathus, the fore feet in that genus being, as compared with the hind 

 ones, unusually large and powerful; e, the very "long hind legs and 

 long tail " are again commented on, "leaving little room to doubt that 

 its habits are similar to those of the jumping mice, Meriones labra- 

 dorius," a comparison not so applicable to a Pocket Mouse as a 

 Kangaroo Rat, in fact not applicable to Perognathus at all, so far as I 

 have examined them; e, the long tail (11 times length of head and 

 body) is applicable to both genera; its absence of crest or pencil 

 usually seen in Perodipus may have been due to immaturity: the so- 

 called "Dipodomys heermanni," of Leconte, from the "Sierra 

 Nevada," does not seem to have had the usual penicillate tail ; /, 

 "color above, sepia brown, beneath, white, a dark line crosses the 

 cheeks beneath the eyes; " to no specimen or description of Perogna- 

 thus I have seen will this characteristic color combination apply, on 



