PORELLA COMPRESSA. 331 



N. H. ser. 3, ix. 308 (50sep.): Smitt, Escharse (auolt.) 

 forma, 1. c. 1867, Bihang, 23 and 149, pi. xxvi. figs. 138, 

 139; Bryoz. from Nova Zembla, I. c. 1878, no. 3, 11 {not 

 Millepora cervicornis of Pallas, nor Eschara cervicornis of 

 Milne-Edwards). 



PoKELLA CERVICORNIS, Gray, B.M. Rad. pt. i. 127. 



? Cellepokaria surcularls, Packard, Invertebr. Labrador, Mem. Boston 

 See. N. H. i. (1867), pt. ii. 



EsciiARA STELLATA, Pettch, Journ. Linn. Soc. Zool. xiii. 481, pi. xxiii. fig. 5, 



Zoarium erect, of a delicate flesh-colour when living, sur- 

 face roughened by numerous prominent cells ; much and 

 irregularly branched ; branches generally more or less 

 compressed, occasionally roundish, truncate or bluntly 

 pointed. Zooecia on both sides of the zoarium, very 

 irregularly disposed (except on the growing extremi- 

 ties of the branches, where they are regular and 

 the surface smooth), ovate, ventricose, rising towards 

 the mouth; surface dense, minutely roughened and 

 punctured with rather large perforations round the 

 margin; the younger cells often with ribs radiating 

 from the side towards the centre; orifice (in the 

 adult state) arched and expanded above, contracted 

 below, sides slanting inwards, a slight constriction a 

 little above the lower margin, forming a sinus in which 

 there is an avicularium, with rounded mandible. Ooecia 

 rounded, more or less immersed, surface smooth and 

 entire. 



Height of fine specimens about 3 inches. 



Range of Variation. In mode of growth there are 

 many variations ; but the minute characters are sufficiently 

 stable. There is, in the first place, a marked difference 

 in habit between southern and northern specimens. The 

 former are much more massive than the latter ; they have 

 usually very broad and thick compressed branches, ren- 

 dered irregular by many nodulous protuberances, which 

 frequently anastomose and occasionally terminate above 

 in somewhat palmate expansions. Shetland examples. 



