Zoology. 649 
erm naked; mouth inferior; lower lip reverted; teeth 
bicuspid, in several series .--.--... Argeidæ 
(dd) Derm with bony plates. 
(e) Caudal vertebral compressed, the neural and hæmal spines 
expanded, forming a continuous ridge above and below. Sides 
with several series of plates; mouth inferior ; lower lip reverted ; 
teeth turned abruptly back above, a single series erect, the inter- 
maxillaries and dentaries box-shaped, filled with numerous de 
relay teeth ; intestinal canal coiled. Cavity of air-bladder usually 
communicating with the exterior at a notch in the posterior margin 
of temporal plate at beginning of lateral line.......... Loricariide. 
„ (ee) Caudal vertebræ normal, the neural and hemal spines spine- 
li ze and separate. Sides with two series of plates; mouth ter- 
minal ; lower lip not reverted ; teeth villiform ; cavity of air-bladder 
communicating with the exterior by means of a long narrow slit in 
le tipora? plitenas nE e ichthyidæ. 
mi eee R. Eigenmann. (Mus. Compar. Zoilogy, Cambridge, 
ass. 
Description oF a New Rep-BAcKED Mouse (Evoromys 
DAWSONI) FROM THE HEADWATERS OF LIARD RIVER, NORTH- 
one | 
Sources of Liard River, in lat. 61° 30’ N.; long. 129 3 wee, ie 
altitude, 3,000 feet. 
, So little is known of the small mammals of this remote and 
inaccessible region that it is not particularly surprising to find that 
the mouse collected by Dr. Dawson proves to be undescribed. In 
Some respects it is intermediate between the cireumpolar Hvotomys 
rutilus and its more southern congener, Evotomys gapperi. But since 
it differs from both and no intermediate forms are wn, it must 
