198 VOLUTHARPA. 



differs in its simple foot and in possessing eyes as well as in den- 

 tition. The form and porcellanous texture of the shell are like 

 Bullia, and serve to separate it from Buccinum. Mr, Arthur 

 Adams says that the animal is like Buccinum, of a white color 

 sparsely sprinkled with black on the head, foot and siphon; the 

 tentacles are broad, close together at the base, and rather short, 

 with the eyes on the outer side, near the middle ; the siphon is 

 thick and short, and the foot is fleshy and simple behind. 



With regard to the Volutharpa ampullacea,a, very remarkable 

 fact may be mentioned. The majority of the individuals are 

 without opercula, even without a trace of the pad-like gland or 

 area from which the operculum is secreted. About ten per cent, 

 of the individuals of the var. acuminata which I have examined 

 had traces of this gland or area, marked b}^ its smooth and 

 rather whitish surface on the granulous dark slate-colored foot. 

 About fifteen per cent, had well developed opercula in the proper 

 position. I have ascertained the same to be the case with regard 

 to the typical form, from alcoholic specimens, collected by Dr. 

 William Stimpson in Behring's Strait. There is no mistake 

 about this, strange as it may and must appear, that different 

 individuals of the same species are indifferently operculate or 

 inoperculate, 



A careful examination of this appendage reveals some singu- 

 larities in it worthy of note. At first the operculum is of an 

 ovoid form, with the nucleus near the edge at the larger end, and 

 increases by additions around the edge, but principally upon the 

 smaller or upper end. However, at some late period of its 

 growth it takes a new start, and, seemingly, a new operculum is 

 commenced underneath the old one, with a central nucleus 

 which increases by annular additions, and finally has its edges 

 very much thickened and turned upward, giving it a saucer-like 

 appearance, while the old operculum seems as if laying upon the 

 saucer, with its nucleus and some of the adjacent portion pro- 

 jecting over the edge anteriorly. It has in all a diameter of 

 1 inch. That its form is not due to an individual abnormality 

 is evident from the fact that all the specimens examined were 

 similar.* 



* W. H. Dall, Am. Jour. Conch., VII, 106. 



