1S90.] MARINE MOLLUSCA OF ST. HELKNA. 263 



from some others which closel)' approach it in outline. Most of 

 the specimens are rather smaller tliaii that of wliicli the dimensions 

 are given ahove, and have an average length of fi| millimetres and a 

 diameter of 2f . All of this smaller form are blotched irregularly 

 with pale brown, and have a more or le<s distinct interrupted pallid 

 zone at the periphery, and white spots below tlie suture. The 

 larger form is ornamented with numerous longitudinal light brown 

 lines, which vary in thickness, and are connected, more or less, by 

 short transverse ones, producing somewhat the appearance of an 

 indistinct network. 



Nassa SANCTiE-HELEN^, A. Adams. 



A series of about forty specimens of Nassa from St. Helena 

 makes it extremely difficult to decide to which species they should be 

 assigned. Some exactly resemble Adams's type (Reeve, Conch. Icon, 

 fig. 1 88), whilst others appear altogether" different, the form and 

 sculpture being very variable. The typical form may be thus 

 described : — Shell elongate, with a rather acutely produced spire, of 

 a dirty whitish colour, with a dark brown line" interrupted by the 

 costae around the middle of the body-whorl, also one above near the 

 suture, and another round the base', both being less clearly defined 

 and not so regularly interrupted as the median line; whorls 8, the 

 three apical smooth, glassy, very convex, the rest narrowly somewhat 

 excavated or concave above, then moderately convex at the sides ; 

 sculpture consisting ot 10-12 slightly oblique strongish costse, a 

 little nodose at the angle of the concavity, and of spiral sulci, which 

 are well defined and cover the whole of the spire, but become a 

 trifle obsolete on the central part of the body-whorl ; outer lip 

 thickened by a broad external varix, marked with a brown spot, the 

 termination of the central interrupted line, and furnished within with 

 about a dozen fine lirae ; columella covered with a callus, with a 

 small elongate narrow tubercle above and several irregular trans- 

 verse rugosities and tubercles from thence downwards. Length ] 2 

 millim., greatest diameter 6|. The principal variations consist of 

 differences of form and colour, in the number of costee, and in the 

 greater or less development of the spiral grooving. When the sjnral 

 sulci are strongly marked, the costte become somewhat nodulous as 

 in N. Incrassatd, Striim, v^ith which species Jeffreys, in his account of 

 Mr. Melliss's shells, associated two specimens obtained at St. Helena, 

 and placed in the British Museum by that gentleman. Not one of 

 the St. Helena shells has the canal stained with black like the 

 majority of specimens of incrassata. 



Nassa cinctella, A. Adams. 

 . Hub. St. Helena, 20 fathoms, sandy mud {Adams). 



The two specimens in Mr. Cuming's collection are all I have seen of 

 this species. It is rather like the West-Indian N. ambiyua of 

 Montagu in its short squarish form, but differs in having less tabu- 

 lated whorls, and stronger or coarser spiral sculpture. 



