280 Proceedings of the Royal Irish Academy. 



not constant at the various levels in any one colony. The anthocodiae are 

 very simple ; the tentacles are short and conical, and bear a siagle row of 

 short, simple pinnules on each side. There are scale-like spicules on the 

 aboral surface of the tentacles. 



The axis is composed of a homy substance impregnated with carbonate of 

 lime. It consists of concentric laminae, which are deposited on the periphery; 

 and it retains its shape on decalcification. 



The spicules are extremely minute, and contain the following types : — 

 (1) Indian club-shaped forms known as clxihs ; (2) dumb-bell foims known 

 as double-clubs; and (3) spindle-shaped forms or sjnndlcs. Intermediate 

 forms such as elongated double-clubs and double-spindles may also occur. 



Qenus Juncella emend. 



Colony simple or branched ; the coenenchyma is usually thick ; the polyps 

 are distributed (1) irregularly over the whole coenenchyma or (2) in definite 

 longitudinal series, defined by the position of a number of main canals, 

 constant for the species. The verrucae (1) may be sunk within pit-like 

 depressions, (2) may be low and dome-like, or (3) may be sub-conical and 

 adpressed to the stem ; all these conditions may appear m one colony. The 

 axis is formed of concentric layers of a horny substance impregnated with 

 lime ; there is usually a more densely calcareous core. 



The coenenchjTna consists of two layers — (1) an outer, containing no 

 canals, in which the polyps are retracted ; and (2) an inner, which is bounded 

 both externally and internally by a circle of small canals, and which is 

 penetrated by a network of small solenia uniting these two series. 



The outer series of canals communicates directly with the polyps. A 

 certain number, two or three, of the canals of the inner series, sj-mmetrically 

 arranged, are larger than the others, and are known as the main canals. 

 Their position defines in most cases the distribution of the polyps. The 

 spicules are extremely small ; they contain clubs, but otherwise are typical of 

 the family. 



Genus Scirpearia emend. 



The colony may be (1) simple and flagelliform, (2) slightly branched, 

 (3) much branche<l and dendriform, or (4) branched in one plane. The 

 branches themselves are usually long and flagelliform. The coenenchyma 

 varies greatly in thickness in the different species. The canal system is 

 typical of the group; so far only species with two or four large main 

 longitudinal canals are known. The verrucae are disposed in a number of 

 longitudinal series, the number of which is the same as the number of main 

 canals. As in Juncella the number of transverse rows in each series varies 



