224 NATICID-^. 



5. N. Alde'ri"*, Forbes. 



X. Alderi, Forb. Mai. Mon. p. 31, pi. ii. f. 6, 7. N. nitida, F. & H. iii. 

 p. 330, pi. c. f. 2-4, and (animal) pi. PP. f. 5, as N. Alderi. 



Body creamcolour, spotted or streaked with, reddish- or 

 purplish-brown : snout broad, thick, and flexible, margined by 

 a line of pnrplish-brown : tentacles sharp-pointed, tipped or 

 edged with the same colour: {eyes, "distinctly visible, im- 

 mersed in the centre of the anterior bases of the tentacula " 

 (Clark) :] foot expansile, minutely veined. 



Shell conic-globose, inclining to oval, very thick and solid, 

 opaque, glossy : sculpture numerous and minute lines of growth, 

 which are not discernible without a magnifying-power ; oc- 

 casionally a few slight spiral stria3 may also be observed : 

 colour buff, adorned with spiral rows of reddish-brown or light 

 chocolate spots and streaks ; of these there are 5 on the body- 

 whorl, and 1 on each of the next two or three whorls ; all the 

 rows except the middle one on the body- whorl (which is com- 

 posed of short zigzag longitudinal streaks) are usually formed 

 of blunt arrow-headed spots, the uppermost row being fre- 

 quently more dark-coloured and conspicuous than the rest; 

 the umbilicus and inner lip are also stained with reddish-brown 

 or light chocolate : epidermis yellowish-brown and somewhat 

 fibrous, preserved within the umbilicus only : spire short, but 

 prominent, ending in a blunt point : ivliorh G, convex, com- 

 pressed, and shelving upwards towards the suture ; the last 

 occupies eleven-twelfths of the spire : suture oblique and 

 slight : mouth equal in length to nine-twelfths of the spire, 

 scarcely expanding, and bluntly angulated at the base : outer 

 lip sloping from the periphery, and having a blunt edge : inner 

 lip broad, forming a very thick ridge or callosity at the upper 

 angle of the mouth, and a large thick pad in the middle, which 

 is obtusely triangular and proj ects over the upper side of the 

 umbilicus; this part is narrow and oblique, two-thirds open, 

 separated on the lower side by a slight ridge, between which 

 and the pad are some obscure and smaller ridges : operculum 

 light-horncolour, striated as in the last species, and marked 

 with a few indistinct revolving lines ; spire defined by an 

 overlapping and raised edge. L. 0-7. B. 0*65. 



Var. 1. lactea. Shell milk-white. 



* Dedicated to Mr. Joshua Alder of Newcastle-on-Tyne, a distinguished 

 British zoologist. 



