THE NATURAL HISTORY SURVEY. 235 
Length, 2.50; diameter, 1.30; aperture long, 1.00 mill. (10289.) 
eer iOs ave Oe ORES ieee “110 “ (10646.) 
Here DOr Scie... ah me whe «90. « (10287.) 
Goo N Fo Aamir st pb tah Sa “110 “ (11995.) 
Animal: Small, white and transparent, except head, neck 
and eye-peduncles which are black; foot narrow and long; eye- 
peduncles long and slender; tentacles conical,short. Respira- 
tory orifice prominent, placed at the angle of peristome and 
body whorl. 
Faw: Long and narrow, slightly arched, the ends a little 
narrower than the central portion and rounded; convex mar- 
gin smooth, concave margin notched, and anterior surface ver- 
tically striated (Fig. 66, J). 
Radula formula: 31,+4+4+4+,2, (11—1—11); central 
tooth with a base of attachment longer than wide and with the 
Fig. 66. 
Radula of BIFIDARIA CONTRACTA Say. (Original.) c, central tooth; 
1, first lateral; 7, third marginal; 9, fifth marginal; J, jaw. 
lower outer angles expanded; reflection small, narrow, tricus- 
pid, the central cusp long, wide, blunt, the side cusps shorter 
and sharper; lateral teeth with a wide base of attachment, ex- 
panded on the lower outer angle; reflection narrow, bicuspid, 
the inner cusp very long and wide, almost reaching the lower 
margin of the base of attachment, the outer cusp about half 
as large and sharp-pointed; marginal teeth low, wide, with 
from three to seven cusps, the single inner being very large 
and sharp, and the outer cusps short. The fifth marginal has 
three cusps, the seventh five cusps and the ninth seven cusps; 
