12 BANGS — LABRADOR MAMMALS [Pe 
Cranial characters.— The skull, compared with the large, massive skull of 
the Canadian form, true / z7bethicus (Linn.), is smaller, narrower, and lighter 
built throughout; rostrum straighter, and proportionally longer and more 
slender; nasals longer and narrower; mandible more slender and of lighter 
build; incisors more slender; molars about the same. 
Measurements.—Type, & adult: total length, 549; tail vertebra, 249; hind 
foot,73 mm. No. 7974, @ adult, from Black Bay, Labrador: total length, 
523; tail vertebree, 234; hind foot, 73 mm. 
Skull, type, @ adult: basal length, 58.4; occipitonasal length, 61.4; 
zygomatic width, 40; mastoid width, 26.6; least width between orbits, 6.2; 
length of nasals, 22.6; greatest width of nasals, 8.4; distance from front of 
molar series to back of incisors, alveoli, 23; molar series, alveoli, 15.6; 
length of single half of mandible, 43.4 mm. No. 7974, @ adult, from Black 
Bay, Labrador: basal length, 53.2; occipitonasal length, 58; zygomatic 
width, 38; mastoid width, 25.2; least width between orbits, 6.4; length of 
nasals, 22.2; greatest width of nasals,8.6; distance from front of molar series 
to back of incisors, alveoli, 21.4; molar series, alveoli, 15; length of single 
half of mandible, 40.6 mm. 
Remarks. It was with some hesitation that I referred, on 
former occasions, the one muskrat from Hamilton Inlet, now the 
type of / sibethicus aguilonius, to the Canadian form, true 
zibethicus. The addition of the three Black Bay specimens proves 
the Labrador form to be separable. It is possible that / zebethicus 
aguilonius is confined to the Labrador peninsula. If, however, it 
is found to the westward, its range must be very northerly. The 
muskrats I collected at Lake Edward, Quebec, do not approach 
it in any way, but are wholly referable to true /. zzbethicus. 
The Labrador muskrat can at once be told from true /& 
zibethicus by its black back, smaller size, and by the cranial 
characters pointed out above. It hardly needs comparison with 
the muskrat of Newfoundland, /. odscurus, that peculiar island 
species being still smaller, with shorter tail, smaller hind foot, 
small, smooth skull, with wide supraoccipital (like the young of 
other forms), small audital bullae and weak molars. 
Microtus enixus Bangs. 
One hundred and forty specimens, of all ages and both sexes. 
This series agrees closely with the type series from Hamilton Inlet. 
There is about the usual range of individual variation in color, 
