480 University of Califorma Publications in Zoology — [Vou. 17 
it the darkest form as yet characterized. Both old and young may 
be separated with certainty on coloration alone from any known form 
of the genus. The anterior dilation of its nasal outline serves to sep- 
arate it from A. r. phaea and A. r. pacifica. From A. r. humboldtiana, 
its nearest neighbor on the north, it is separated by its darker color- 
ation and, in general, smaller size. 
CRANIAL MEASUREMENTS OF Aplodontia rufa nigra (1 CRANIUM) 
Basilar: len oth’ ic. 82 ics acsncsaten anes se oe eae eee eee 57.1 
Tengphion nasalls' ts: e ee ee ene ee 23.2 
Width of nasals ......... 11.0 
Length of audital tube ....... aU 
Length of incisive foramen 
ZY FOMAtIC wpb) Severe eeceesee ees eee 
Greatest width of interpterygoid fossa 
Mastoid width of cranium ....................... 
Alveolar length superior cheek teeth -. 
Distance between infraorbital foramina _.. 
Mandible, transversely across angular process ..... 
Mandible;yoreatest lengthy =. ere ee 
oO 
OS) Me ol ed oor) 
Paw ODN OW 
HB DORR OF 
EXTERNAL MEASUREMENTS OF Aplodontia rufa nigra (1 SK) 
Motallen'gbhies wesc 346 
PLN hy POO 1 2 Seo sack sence cen eee see eons 55 
That Aplodontia rufa nigra finds in A. r. humboldtiana and in 
A. r. phaea its nearest relatives seems reasonably clear. The blackish 
coloration of the Point Arena form suggests the dark coloration of 
the Humboldt Bay race, while its size and the length of incisive fora- 
mina of the skull show that it is not far from phaea. 
The distinctive coloration of all the known specimens of A. r. nigra 
and its geographical isolation constitute, perhaps, arguments for its 
recognition as a full species. On the other hand, the paucity of 
material representative of the form, coupled with the amplitude of 
individual variation in other forms in the genus, and with the evident 
overlapping of cranial characters with humboldtiana on the one side 
and phaea on the other, indicate the propriety, for the present at least, 
of allocating 2igra as a subspecies of rufa. 
Aplodontia rufa phaea Merriam 
Point Reyes Aplodontia 
?Haplodon rufus, True (1885), p. 596. 
Aplodontia phaea Merriam (1899a), p. 20. 
Haplodontia phaea, Elliot (1901), p. 114. 
Type.—Male adult, skin and skull; no. 186475, U. S. Nat. Mus., 
Merriam Coll. (no. {)); Point Reyes, Marin County, California; 
August 1, 1886; collected by C. A. Allen; orig. no. 142. 
