THE NATURAL HISTORY SURVEY. 213 



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.) 

 ", 4.00; " 3.75; " 1.50; " " 1.75 " (10126.) 



Animal: 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). 



r^i 



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. 



Jaw: Long and narrow, ends sharply attenuated; dorsal 

 border rounded, smooth; ventral border with a large, rounded, 

 median projection; anterior surface striate, the striae con- 

 verging toward the median projection (Fig. 51, J). Professor 

 Pilsbry (Guide to Helices, PI. xv, Fig. i) 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: f +f +i+f+i+f +i+f+f (12- 1 - 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 



