THE NATURAL HISTORY SURVEY. Pan We 
sion, and exhibiting all the volutions almost as clearly as on 
the upper surface, and showing also very distinctly the oblique 
lines of growth. 
Gr. diam., 3.75; lesser, 3.50; height, 1.50; umbil. diam., 1.75 mill. (10929.) 
ar wie: AON ee BB.) = P50. “195 © — (10126.) 
Anmal: With a long and narrow foot, deeply furrowed 
on the dorso-posterior portion; tentacles short and thick; eye- 
peduncles not long, thick and club-like; mantle thin, simple; 
color whitish, with pure white patches scattered about causing 
a mottled appearance. Shell placed well toward the posterior 
part_of the body, and carried almost flat (Fig. 50). 
To 
Fig. 51. 
Radula of HELICODISCUS LINEATUS Say. (From nature, after Bin- 
ney.) c, central tooth; 1, first lateral; 5, fifth lateral, modified; 8, 11, mar- 
ginal teeth, 
Faw: Long and narrow, ends sharply attenuated; dorsal 
border rounded, smooth; ventral border with a large, rounded, 
median projection; anterior surface striate, the striz con- 
verging toward the median projection (Fig. 51, J). Professor 
Pilsbry (Guide to Helices, Pl. xv, Fig. 1) figures a jaw with 
rounded ends and very arcuate. The specimens examined by 
myself seemed to be more like Morse’s figure, although there 
was some variation. 
Radula formula: $+%+4+4+4+4+4+ 9+3 (12-11-12); 
central tooth with a base of attachment longer than wide, the 
lower outer corners produced into small, narrow projections; 
reflection narrow, tricuspid, the central cusp longer than the 
two side cusps; lateral teeth with a wide base of attachment, 
almost square in fact, the lower right outer corner with a 
