MUCRONELLA PEAC11II. 3<>l 



Zocecia rhomboid, not separated by deep sutures, gene- 

 rally arranged quincuncially, granular or smooth, punc- 

 tured or areolated round the margin ; orifice suborbi- 

 cular, longer than broad, well arched above, with ii 

 slightly raised and thickened peristome, which is pro- 

 duced in front into a pointed mucro, a small bifid den- 

 ticle within the lower margin, and six slender oral 

 spines. Ocecia small, globose, erect, with two spines 

 in front, on each side. 



Colonies forming large irregular patches Fj 16 



of solid texture, which generally pre- 

 sent a very flat and uniform surface. 



Primary cell with somewhat circular 

 aperture, occupying the upper portion 

 of the front surface, surrounded by 

 about nine spines ; covering membra- Primary cell, 

 nous (woodcut, fig. 16). 



Var. a (labiosa, Busk). Zocecia ovate, distinct, more 

 deeply divided than in the ordinary form, disposed in 

 lines, smooth ; orifice much raised, the front lip everted 

 and much thickened and produced. (Plate LI. fig. 1.) 



Var. /3 (octodentata) . Zocecia ovate, distinct, convex, 

 smooth, disposed very regularly in linear series ; orifice 

 rather small, with a pointed mucro in front and eight 

 marginal spines. Ocecia globose, prominent, set very 

 far back, all the spines in front of it. (Plate LI. fig. 2.) 



RANGE OF VARIATION. This species presents many diver- 

 sities of appearance, due to age and locality ; but there 

 seems to be a very moderate amount of variation in the 

 more important characters. In young specimens the cells 

 are smooth and shining, and bristle with their long and 

 slender spines. With age, and in deep-water localities, 

 the silvery sheen is lost ; the cells are thickened, and 

 usually of a dull whitish colour, the surface of the zoarinm 

 is flat, the shallow sutures between the cells being almost 



