452 University of California Publications in Zoology — [Vou 17 
2. Tur Genus Aplodontia 
2 
1 
3 ; ; ; 
we x 222; permanent teeth hyposodont, of secondarily simple 
The chief generic characters are as follows: dentition ite+ 
enamel pattern, characterized by prominent styles internally on the 
inferior teeth and externally on the superior teeth; cranium greatly 
depressed; postorbital processes on frontal absent; postorbitals on 
jugal weakly or not at all developed; infraorbital foramen primitive, 
not transmitting any part of masseter; angle of mandible remarkably 
expanded transversely ; seaphoid and lunar not separate; fibula not 
articulating with caleaneum, free from tibia; body stout, about 350 
millimeters long; pelage dark; eyes and ears small (pl. 29) ; mammae 
six; tail very short; nocturnal, fossorial, found in restrieted area in 
western North America. 
The much modified hyposodont teeth, the depressed skull, the 
absence of postorbital processes (pls. 26, 27), the extraordinarily 
inflected angle of the mandible, the fusion of the scaphoid and lunar 
into a single bone, the proportionate enlargement of the forefeet (for 
digging), and probably also the smallness of eyes and ears, are sug- 
gestive of a high degree of specialization in Aplodontia. On the other 
hand the simplicity of the dental formula and the characters of the 
infraorbital region (pl. 27) show a generalized or primitive condi- 
tion. The infraorbital foramen is moderate in size, and does not 
transmit any portion of the masseter, the origin of which, according 
to Matthew (1910, p. 69), is wholly behind and below the lower 
margin of the orbit, and not extended forward on the side of the 
muzzle. 
3. VARIATIONS IN THE GENERIC NAME 
Palmer (1904, pp. 24, 25) has ealled attention to the fact that the 
name Aplodontia is capable of twenty-four modifications, each one 
progressively differing from the next by a single letter. That several 
of these possible spellings of the name have found place in literature 
is indicated by the following list of names applied to the genus: 
Anisonyx (part) Rafinesque (1817), p. 45. 
Anisonix (part) Minding (1829), p. 86. 
Aplodontia Richardson (1829a), pp. 333-337. 
Apludontia Fischer (1830), p. 398 (error for 598). 
Haplodon Wagler (1830), pp. 4, 22. 
