MUCRONELLA VENTRICOSA. 363 



Exped.) : Bahusia, common, on marine plants in the lit- 

 toral region chiefly (Smitt) : Bergen (A. M. N.) : Mar- 

 souin, Gulf of St. Lawrence (Dawson) : Adriatic, rare 

 (Heller). 



RANGE IN TIME. Coralline Crag, very abundant (S. 

 Wood) : Middle Pliocene beds (Suffolk Crag) ; Upper 

 Pliocene ; Palaeolithic (A. Bell) : Scotch Glacial deposits 

 (Geikie). 



MUCRONELLA VENTRICOSA, Hassall. 

 Plate L. figs. 6-8. 



LEPRALIA VXKTRICOSA, ffass. Ann. N. H. ix. 412 : Johnst. B. Z. ed. 2, 305, 

 pi. liv. fig. 5 : Busk, B.M. Cat. ii. 78, pi. Imii. figs. 5, 6, 

 ? pL Imiii. fig. 5 (not pi. ici. figs. 5, 6) ; Crag. Pol. 49, pi. 

 yi. figs. 3 & 6 : Manzoni, Bryoz. Mediterr. Suppl. Contr. i. 

 7, pL iii. fig. 1. 



DIBCOPORA COCCIXEA, forma VENTRICOSA (part.), Smitt, 1. c. 26 & 172, pi. 

 xxvii. fig. 172 (?). 



LEPRALIA ARRECTA, Betas, FOBS. Bryoz. 68terreich.-nngariflch. Miocana, 24, 

 pL ii. fig. 11. 



Zocecia rhomboid or ovate, or subglobose, distinct, convex, 

 divided by deep sutures, contracted and more or less 

 suberect above, usually disposed very regularly in linear 

 series ; surface granular, and often traversed by radia- 

 ting furrows, a single row of punctures round the base ; 

 orifice suborbicular, a large bifid denticle within the 

 lower margin; peristome raised and thickened, rising 

 in front into a broad, prominent mucro, which is some- 

 times bifid ; marginal spines four, stout, two on each 

 side. Ocecia globose, closely united to the cell above, 

 smooth or subgranular, with one or sometimes two 

 spines in front of it, on each side. 



Colonies of a greyish-white colour, often silvery and 

 glistening, forming large crusts, which frequently as- 

 sume a lobate figure. 



