346 MOLLUSCA OF THE ' challenger' EXPEDITION, 



This is a long and narrow shell witli little of the generic pecu- 

 liarity of shape, though the anterior splay form is recognizable. 

 The singular thickening of the pillar seems to increase with 

 age. In the three specimens from St. 78 it is much more strongly 

 marked than in the somewhat younger shells from St. 73. The 

 young shells of S. punctostriatus, Mighels, are squatter, rounder, 

 with a flatter crown, and have the outer lip less produced behind ; 

 their stippled sculpture, which varies a good deal, is often 

 coarser, and forms more continuous spirals ; the pillar-lip, too, and 

 shape of the body are very different. In one of the St. 78 speci- 

 mens in particular the slow wasting away of the surface has 

 scarely attacked the stippled pits of the spirals, which accordingly 

 remain projecting as flat round tubercles. 



Fam. Apltsiidje, d^Orh. 

 Gen. DoLABEiFEEA, Gray. 



DOLABEIEERA TETANGULAEIS, U. sp. 



Oct. 29 to Dec. 16, 1873. Simon's Bay, Cape of Grood Hope. 

 10-20 fms. 



Shell. — Much arched, corrugated, porcellaneous, dull, and scored 

 on the upper surface with sharj) strong lines of growth, on the 

 under surface lustrous and amorphous, with a strong but irregular 

 oblique longitudinal furrow and rough radiating lines toward 

 the back ; it resembles the blade of a fleam, being triangular, 

 with a straight back, the handle (where the nucleus is) in front, 

 and the point (a bluntly rouaded one) on the left. Bound the 

 nucleus there is an amorphous expansion and thickening ; across 

 the blade obscure and unequal rays diverge from a point behind 

 the nucleus. The back of the blade is thick and blunt, the 

 other two sides bluntly bevelled to a sharp edge. H. 0*43. 

 B. 0"21. Height of the arch 0"1. G-reatest breadth behind 0"3. 

 This species is much more attenuated in front than D. mar- 

 morea, Pease, from the Sandwich Islands, which otherwise it much 

 resembles in form and texture, whilst it is in sculpture much 

 more delicate. D. Maillardi, Desh., from the island of Bourbon 

 (see ' Moll, de Bourbon,' p. 53, vii. 20-22), is much more regular 

 in shape, more like the seed of our common plane {Acer pseudo- 

 plataiius), with a regular-shaped wing and a head or nucleus 

 continuous with the body instead of, as here, a fleam-like blade 

 and distinct handle. 



