1890.] MARINE MOLLUSCA OF ST. HELENA. 207 



superne suturam haud attingens ; columella inferne triplicata, 

 plica suprema minima, interdum subobsoleta, 

 Longit. 2k millim., lat. 1|. 



M. lavalliana of d'Orbigiij', a common 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, lavis ; spira obtti- 

 sissima, vix data ; apertura angusta ; labrum paulo inflexum et 

 incrassatum, superne suturcejunctum, intus haud denticulatum ; 

 columella quadriplicata, plica suprema minutissima. 

 Longit. 1| millim., lat. 1. 



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

 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 few additional denticles or plicse at the upper 

 part. 



Cassis testiculus, var. 



Hab. West Indies. 



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

 Bruguicre. 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. Tnrton 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. aquutilis. In 

 ^ Japan, Meeres-Coiicbyl. part i. p. 48. 



