MURIDAi— SIGMODONTES—NEOTOMA. 13 
We tabulate none of the very young skulls before us, as these would 
vitiate the results, especially as regards the lengthened muzzle of the bushy- 
tailed species; the young of that animal not having the snout noticeably 
different from that of the rest. The difference in length of snout between 
cinerea and floridana does not.seem to be much from the figures; but a tenth 
of an inch on the end of a rat’s nose is something; and, viewing the naked 
skulls, the rostral part in cinerea is seen to be slenderer, as well as longer, 
than it is in floridana; the interorbital space is more constricted and more 
deeply indented. -Aside from this, the skulls show nothing diagnostic among 
the several real or supposed species. Adult ones average about two inches 
long (1.84 to 2.10) by an inch broad (0.84 to 1.12) across the zygomata, and 
barely over two-thirds of an inch in height (taken as described—see under 
Tab. 1, p. 12). The extreme length of the under jaw is about an inch anda 
fourth on an average, but runs from 1.10 to 1.45; a part of this difference 
being due to the fluctuating length of the under incisor. This generally 
protrudes one-half of an inch, or a little more; the upper incisors protrude 
about one-third of an inch. The molar series is from three- to nearly four- 
tenths of an inch long; thereis nothing diagnostic in its length. 
In connection with the rostral elongation of the skull of NV. cinerea, we 
should note another slight peculiarity—not, however, diagnostic of species, 
much less of sections of the genus. In all the western skulls examined, includ- 
ing even those of NV. floridana, there is a tendency to a narrowing of the con- 
duit of the posterior nares by more or less filling in of bone from the alveolar 
border. Thus, in ordinary South Atlantic floridana, the whole palate is defi- 
cient behind the point indicated in the generic diagnosis—nothing bounds 
the space on either side but the alveolus itself. In the other extreme, there is 
quite a little shelf on either hand, noticeably narrowing the aperture. But 
the feature is extremely variable, and cannot be relied upon for even specific 
diagnosis. 
We know ¢hree good North American species of this genus: first, there 
is the ordinary N. floridana, really inhabiting most of the United States, 
except New England, though decidedly southerly, and ranging thence into 
Mexico; secondly, the NM. fuscipes, which appears to be perfectly distinct, 
and is a highly interesting animal, opening the way, through several of its 
features, into the tropical aspect of the genus, such as is exhibited by the 
N. ferruginea of Tomes, from Guatemala, and furnishing an analogy to the 
