1890.] MARINE MOLLUSCA OF ST. HELENA. 2G7 



superne suturam haud attingens ; columella in/erne triplicata, 

 plica suprema minima, interdum subobsoleta. 

 Longif. 2| millim., lat. \h- 



M. lavalliana of d'Orbignj', a commoa West-Indian species, 

 appears to more closely resemble this than any other. That form 

 is, however, a little more solid, hardly so narrow, and has four or 

 more folds on the columella. 



Marginella (Volvaria) atomus. (Plate XXIII. fig. 12.) 



Testa minuta, pyriformi-ovata, alba, pellucida, Idevis ; spira ohtu- 

 sissinia, vix elata ; apertura ayigusta ; labrum paulo inflexum el 

 incrassatum, superne suturcB junctuju, intus haud denticulatum ; 

 columella quadriplicata, plica suprema minutissima. 

 Longit. Ig millim., lat. 1. 



This species might almost be regarded as a small form of the 

 Australian M. angasi, from which it seems to differ chiefly in size. 

 The columella of that species is not quite the same, however, being 

 furnished with a k^ additional denticles or plicae at the upper 

 part. 



Cassis testiculus, var. 



Hab. West Indies. 



The St. Helena form of this species is that named C. crumena by 

 Brugniere. From the series of specimens examined, I am inclined 

 to think that it cannot be held distinct. It appears to exist on the 

 eastern side of the Atlantic, and has not, I think, been recorded from 

 the western parts. The typical form, however, of C. testiculus is 

 known from the West-African coast, and a specimen from that 

 region was presented to the Museum by F. P. Marrat, Esq. 



Triton tritonis (Linne). 



Hab. W. Indies, Mediterranean, N. Australia, Pacific Islands. 



A single specimen in a very worn and broken condition, and 

 which, when perfect, must have been about twelve inches in 

 length, is all that was found by Capt. Turton at St. Helena. 

 Mr. Melliss "obtained two living specimens which came ashore 

 at Lemon Valley." The species occurs also at the Canary and 

 Cape de Verde Islands, and it is well known from the West-Indian 

 region. T. seguenzce, Aradas and Benoit, is, in my opinion, the 

 Mediterranean variety of this species. 



Triton olearium (Linne). 



Hab. New Zealand, Port Jackson, Japan, Tahiti, West Indies, 

 Mediterranean, &c., &c. 



The distribution of this species is truly remarkable, and has been 

 ably discussed by Lischke^. 



The specimens from St. Helena have the spiral ridges much more 

 prominently nodose than usual, the varices are thicker, and the 

 labrum not effuse, but very solid and strong as in T. aquatilis. In 

 ' Japaii, Meeres-Cpncbyl. part i. p. 48. 



