S'I'kphknson — Certain Actiniaria collected o{}' Ireland. 14? 



higher and more complex ones the enclocoels. The height and narrowness of 

 the ridges and the depth of the furrows between them make the course of the 

 muscle-layer very sinuous. This layer varies greatly in thickness in different 

 parts, following out very regularly and markedly the rule which prevails in 

 the other two species of Chondrodactis, already described, and which will be 

 apparent on reference to the figure. The mesenterial insertions lie just 

 opposite the bottoms of the furrows, and the layer generally shows a slight 

 narrowing opposite these, as well as its other narrowings over the endocoels. 

 In the places where the layer is well developed (on the exocoelic ridges'', it is 

 very broad and constitutes a large proportion of the thickness of the disc. 

 I is structure is unusual ; it lies altogether outside the mesogloea, between 

 that and the, ectoderm. In its thinnest parts, over the middles of the endo- 

 coels, it forms a single row of ectodermal processes as usual ; but in its better 

 developed parts it is a beautiful, tine network, which appears to be formed by 

 a good deal of anastomosis between very long, branched, ectodermal processes 

 (PI. XVI II, tigs. 19,20). 



In the tentacles (IT. XIX, tigs. 2 and 8), the musculature is ectodermal 

 and well developed. There is a distinct nerve-layer, and spirocysts as usual 

 are present. The tentacles are often longitudinally fluted, and then of course 

 they show, in section, ridges and furrows : the musculature is typically best 

 developed on the former. The ectoderm and musculature are, as usual, reduced 

 on the basal swellings, the mesogloea being enormously developed. "Where 

 well developed, the processes are fairly high, but not specially so, and may be 

 simple or branched ; they are rather stout, and have a characteristic somewhat 

 tufted and fuzzy appearance. 



(iv) The form of the oral disc, and the type of its musculature, as well as 

 most of the other details of its structure, should easily distinguish this species 

 from the rest of the genus. 



Actinauge 1 Verrill. 



Ghondractiniinae with the body always more or less distinctly divided 

 into sewpus and capitulum-. wall generally tough and cartilaginous, very thick 

 or very thin according to state of distension, &c. ; the scapns is tuberculate, 

 and the tubercles are not usually regularly arranged ; they may or may not 

 be tipped with cuticle ; at least twelve " coronal " tubercles are recognizable 

 where the capituluin and scapusjoin, though they may be poorly or irregu- 

 larly developed, and not different from the other tubercles. The capituluin 

 is nearly always free from cuticle, and is provided as a rule with twelve (or 

 a multiple of twelve) ridges, distinct or feebly developed, and very variable 



1 See foot-note on p. IIS. 



[</2] 



