MOLLUSCA OF THE ' CHALLENGEE ' EXPEDITION. 713 



barely angulated at the periphery. Fillar-lip straight, patulous, 

 right-angled at its junction with the base. TJinhilicus small. 

 H. 0-14. B. 0-2, least OIG. Penultimate whorl 0-025. Mouth, 

 height 0-09, breadth O'll. 



The specimen from which I have described this is neither full- 

 grown nor perfect, but the species is a very well-marked one. It 

 is much more depressed and has the whorls less rounded than 

 T. (M.) nitens, Jeffr. Than T. helicinus, Pabr., it is much more 

 depressed, much more brilliantly nacreous, and the surface is 

 much more polished, and the radiating puckers are much stronger. 



I have put a query to Margarita as the group to which this 

 should be attached, because it has not a rounded mouth ; but there 

 is no other group of Trochiis to which it can so well be attached, 

 and none of the characters by which Margarita is defined are very 

 constant. 



1. TuEBo (Calcae) henicus, W. (emKos, unique.) 

 St. 173. July 24, 1874. Lat. 19° 10' S., long. 179° 40' E. 

 Matuka, Fiji. 315 fms. 3 specimens. 



Shell. — Conical, high ; whorls flattened, sculptured, wdth a spi- 

 nose carina, below which the suture is deeply channelled, scarcely 

 coloured. Sculpture. Spirals — below the suture is a flat shoulder, 

 the edge of which is angulated and bordered by a row of largish, 

 white separate beads ; on the flat slope of the last whorl are six 

 rows of smaller separate beads, the highest row" being the largest ; 

 they are not connected by a thread, and the intervals between 

 the rows are about half the breadth of the beads. At the peri- 

 phery is a sharp, expressed, stellate carina, the sharp, hollow, 

 compressed spines of which are about twelve in number. Below 

 the carina the whorls ai'e somewhat constricted, and the contour- 

 line here is perpendicular; on it are four rows of fine beads. 

 The edge of the base is sharply angled and defined by a second 

 smaller, sharp, expressed carina which meets the outer lip j it 

 rises in from thirty to thirty-five vaulted scales, which toward the 

 mouth become like spines. On the flat base are ten very regular 

 rows of separate beads, which are a little stronger toward the 

 middle, and the outermost one of which tends to become scaly. 

 The centre is occupied by a polished, slightly ridged, porcellanous 

 pad. Longitudinals — below the suture and between the beads there 

 are many irregular puckerings following the lines of growth. 

 Colour a light yellowish ruddy tinge, the base paler than the 



