MUCRONELLA ABYSSICOLA. 369 



cell, whereas that of M, variolosa is prominent and con- 

 spicuous. The ovicells also seem to be less immersed. 

 The walls of the cells are thick, and the surface is strongly 

 granulated. 



In general appearance the two forms certainly differ 

 considerably ; but, as Norman has remarked, " it is diffi- 

 cult to point out the distinction in words." 



MucRONELLA ABYSSICOLA, Norman. 



PlateXXXVIII. figs. 1,2. 



Leprai.ia ABYSSICOLA, Nomian, Shetland Pol., Rep. Brit. Assoc. 1808, 307. 



Zooecia large, distinct, broad in the middle, and tapering 

 off towards each extremity, moderately convex, divided 

 by well-marked sutures ; surface minutely granular ; 

 orifice small, terminal, transversely elongated ; the lower 

 margin much raised, slightly bent outwards, forming a 

 screen before the aperture, a wide denticle set deeply 

 within it ; upper margin not elevated, bearing two or 

 three rather stout spines. Ooecia globose, tumid, broader 

 than long, minutely granular, occasionally a small trans- 

 verse rib just above the mouth ; two spines visible in 

 front. 



Colonies forming large, white, glossy crusts, of irregular 

 growth, on which the cells show very distinctly. 



Habitat. On stones, &c., from very deep water. 



Locality. Shetland, to the N.N.W. of Unst, in 140-170 

 fathoms (A. M. N.). 



Geographical Distribution. Gulf of St. Lawrence 

 (Dawson) . 



The cells in this species are almost lozenge-shaped. In 

 the centre they bulge out and attain a considerable breadth, 

 but taper oft' above and below it, terminating in a point at 



2b 



