EEPOET ON THE GASTEEOPODA. 89 



■with very close and numerous lines of growth. Colour yellowish translucent white, with 

 a dull all-pervading nacreous gleam. The strong cord which fills the umbilicus is white, 

 as is also the apex. Spire high, scalar, the separate whorls being a good deal sunk into 

 one another, as well as flattened below the suture. Apex small, rounded, the minute 

 embryonic 1^ whorl barely projecting. Whorls 6, of regular increase, slightly flattened 

 below the suture, rounded on the contour, barely contracted round their base ; the last is 

 faintly angulated at the periphery, and not much rounded on the base. Suture strongly 

 marked by the contraction of the whorl above and the margination below. Mouth oblique, 

 round. Outer lip sharp but strong, porcellanous on the edge, brilliantly nacreous within ; 

 it descends very slightly. Pillar-lip) thick, white, bent nearly to the point of the pillar 

 over the umbilicus. It would be reverted but for the great thickness of the spiral pad, 

 which comes twining up behind it out of the umbilicus, and out of which, at the point of 

 the pillar, it forms a flat, triangular, tooth-like expansion. Umbilicus a minute spiral 

 hole, which twists in between the overlying pillar-lip and the umbilical pad ; the edge is 

 corrugated with the old lines of the lip. H. 0"33 in. B. 0-4, least 0'3. Penultimate 

 whorl, 0-1. Mouth, height Cr2, breadth 0-17. 



This species somewhat resembles in form Trochus tumidus, Mont. ; but, apart from differences of 

 texture, colour, and sculpture, it is much less angulated and less broad on the base than that, and the 

 upper whorls are more tumid and more immersed. Trochus {Margarita) grcenlandicus, Chemn., it also 

 resembles in form and size ; but apart from all differences of colour and sculpture, it is, than that, 

 less conical, more scalar, the suture is much more impressed, and the whorls are more immersed. 

 From Trochus {Margarita) rhina, Wats., it differs in the whorls being much more tumid and the 

 general form less conical. From Trochus (Margarita) pompholugotus, Wats., it differs in the last 

 whorl being far less tumid and out of proportion to those which precede. In contrast with Trochus 

 (Margarita) dnophcrus, Wats., the pad on the pillar- lip is here rather on the outside, with the lip 

 flattened out upon it, while in that species the thickening is on the inside, filling up the lip. There 

 is a general resemblance to Trochus marginulatus, Phil., but the whole sculpture is quite different ; 

 especially on the base that species has a sharp umbilical carina, and a wide funnel-shaped though 

 shallow umbilicus. Taken in general, it most of all resembles Trochus (Margarita) varicosus, Migh. 

 ( = Trochus polaris, Daniels). Compared to that this species is stronger in the shell, and much more 

 distinctly sculptured. That other is higher in the spire, narrower, with a higher and more tumid 

 body whorl ; the whole sculpture, though quite of the same type, is feebler ; the base is more flatly 

 conical, more radiatingly striate with a large funnel-shaped umbilicus which has a double cord round 

 its edge ; the embryonic apex is much larger and coarser, and is altogether more prominent, and 

 consists of nearly one whorl and three-quarters, and the whole shell is in every way larger, with 5f 

 whorls against 6 here. 



(ZOOL. CHALL. EXP. — PART XLII.— r 1885.) Tt 12 



