RISSOA. 17 



what I said iii the Introduction to this work (vol. i. 

 p. xlvii) , viz. that the nucleus of the shell often famishes 

 the conchologist with an important character for dis- 

 criminating species. This part, in fact, represents the 

 earliest stage of growth, before external conditions have 

 had any power in influencing or modifying the structure. 



8. R. punctu'ra^, Montagu. 



Turbo punctura, Mont. Test. Br. p. 320, t. 12. f. 5. B. punctura, F. & 

 H. iii. p. 89, pi. Ixxx. f. 8, 9. 



Body yellowish, streaked with purple (marked with a small 

 red dot under the neck near the eyes, Clark) : mantle furnished 

 at each upper corner of the aperture of the shell with a short 

 cylindrical process : tentacles thread-shaped, rather short, in- 

 distinctly ringed, scalloped at the edges, and sparsely but finely 

 setose : eyes slightly raised : foot squarish in front, and 

 bluntly pointed behind : (opercular lohe very pale muddy-red- 

 dish-brown, and having on each side, close to the junction of 

 the foot with the rest of the body, an irregular, rather large, 

 dusky or lead- coloured stripe, Clark) : appendage simple and 

 short. 



Shell conic-oval (in some specimens more oblong), rather 

 solid, nearly opaque, and somewhat glossy : sculpture, nume- 

 rous fine longitudinal and spiral ribs or striae, which by their 

 decussation form minute squares, and are muricated at the points 

 of intersection ; the longitudinal ones are shghtly curved and 

 do not reach to the base ; the labial rib is more or less thick, 

 according to age, and it occasionally leaves one or two varicose 

 excrescences on the body-whorl ; sometimes it is placed close 

 to the mouth, and at other times at a short distance from it ; 

 the spiral ribs or striae are thread-like and usually are more 

 conspicuous than the others ; the uppermost whorls exhibit 

 under the microscope a few rows of punctures : colour dirty 

 white, often tinged with yellow or reddish -brown, and now 

 and then having the last whorl j^artially spotted or double- 

 banded with the latter hue ; there is frequently also a blotch 

 of reddish -brown outside the mouth, and a similar stain on the 

 pillar-lip : sjnre pointed, usually rather elongated, rarely very 

 short : ivhorls 6, convex, the last occupying about three-fifths 



* From its punctured surface ; h'terally, a pricking. 



