408 CELLEPOBrD^E. 



localities, having been passed over probably from its super- 

 ficial resemblance to C. pumicosa. So far as habit and 

 general appearance are concerned, it affords a striking il- 

 lustration of the protean character of its tribe, the crust 

 being moulded on the various substances which it invests. 

 It incloses the stem and branches of zoophytes in a stony 

 cylinder, which is often nodulated on the surface. I have 

 in my possession a remarkable specimen, which forms a 

 thick-walled tube about two inches in length, round the 

 case of an annelid, and is covered with prominent papillae. 

 On shells the crust rises into mound-like masses, often 

 with a mamillated surface ; it is sometimes of very great 

 thickness, and composed of many strata of cells. The 

 cells are punctured round the edge ; and in certain condi- 

 tions of the zoarium this character is a very conspicuous 

 one; they are also crowded and very irregularly placed. 

 The sinus on the lower margin of the orifice is broad 

 and pointed. When the ovicell is absent the peristome is 

 very slightly developed ; but in fertile cells it rises to a 

 considerable height, and unites with the ovicell, walling 

 in and concealing the primary aperture. 



The surface of the zoarium offers a bewildering profu- 

 sion of structure. Amongst the cells of the uppermost 

 layer those of the one beneath it are more or less visible ; 

 and at all points there are multitudes of the large rostra, 

 avicularia of various form and size, punctured ovicells, 

 now prominent, now deeply immersed, all crowded toge- 

 ther, as it were, without plan or order. The small lateral 

 avicularia in front of the ovicell are often wanting ; but 

 they must be regarded as a characteristic feature of the 

 species. The spatulate avicularia are developed in great 

 quantity; they are met with on all parts of the zoarium, 

 showing no regularity of arrangement, turned now in one 

 direction, now in another ; but in many cases they seem 



