GASTEROPODA. 33 



Being a solitary specimen and surrounded by this uncertainty T have not ventured to 

 assign it as a new species, preferring to give it as a variety, heliciformis, of N. helicina ; 

 but should more specimens occur maintaining its characters that varietal name might be 

 assigned to it specifically. 



In Tab. IV, fig. 12, of ray first Supplement, is represented a specimen under the 

 name of N. proxima, S. Wood, and at p. 74 of the same Supplement, the shell so repre- 

 sented is referred to the species figured in Tab. XVI of my original work under that name. 

 As, however, the specimen in question does not show the depression on the upper part of 

 the volution, and seems to be identical with the shell above given as iV. triseriata, this 

 reference was, I now consider, erroneous ; and the figure should be regarded as one of 

 the last-named species. 



Am AURA HEST-ERNA, S. Wood. Figured in the margin. 



Axis. \ of an inch. 



Locality/. Crag, Boyton. 



Spec. Char. Testa turritd, elongato-conoided, nitidd, glabra ; apice obtusdet dspressd ; 

 anfractibus convexiusculis 5 — 6; suturis distinctis ; aperturd brevi pyriformi: labro 

 acuto simplici. 



Mr. Robert Bell has sent me a specimen, but without a name, which he says came 

 from Boyton, and which appears to belong to the same genus as the specimen figured in 

 my first Supplement under the name of Amaura Candida, Tab. I, fig. 3, from the Red 

 Crag of Butley, and of which a very perfect specimen was also obtained by Mr. Crowfoot 

 from the locality of Boyton. This latter specimen, however, was stained with the Red 

 Crag colour as much as was the Butley specimen, and undoubtedly 

 belongs to the Red Crag. The specimen I am now describing^ 

 however, though evidently of the same genus, is not only 

 specifically different from Candida, but is unstained with any red 

 colour, for it is polished and nearly colourless. It has the two 

 apical volutions shallower and more depressed comparatively to 

 the others, the suture distinct and somewhat deep, the aperture Amaura hestema, 5. roorf, 



1 • enlarged \. 



elongately ovate, terminating acutely at the body oi the volution, 



the outer lip sharp and simple, Avith a small but distinct umbilicus, and the body whorl 



occupies more than half of the entire shell. 



This and Candida are the only species of the genus at present known to me. Their 

 generic character is particularly indicated by the uppermost whorls that succeed the apex 

 being unlike those which follow them, for instead of maintaining the proportions with 

 which the shell commences to grow, the whorls increase in depth far beyond the pro- 

 portions due to the increasing size of the animal, so that the angle of volution becomes 

 greatly diminished. In fact, the Mollusc appears to begin life under the form of Natica, 



5 



