THOMSON AND MACKINNON— STOLONIFERA, ETC. 



199 



dichotomy. Smaller branches may arise singly, especially from the internodes ; they 

 tend to come off at a considerable angle from the parent branch, and it is to them that 

 the anastomosis with neighbouring branches is mainly due. 



The surface of the branches has a glistening, highly " arenaceous " appearance. 



The polyps occur mainly on one face, and over nodes and internodes alike. They 

 project in very distinct verrucse, which show no definite arrangement. 



The polyp-opening is marked by eight lobes of varying distinctness : within these the 

 folded tentacles may be seen ; they are of a greyish tint, and are supported by several 

 spicules placed longitudinally. Stripped of the thin brown coenenchyma, the axis shows 

 relatively long calcareous internodes (5-10 mm.), longitudinally grooved and of a deep 

 cream-colour; the horny internodes are short and scarcely swollen (2x1 mm.); their 

 colour is yellowish-brown. 



The spicules of the cceuenchyraa are mostly spindles and clubs, pale brown 

 and yellowish. The spindles are straight or slightly bent (-17 X '034, -263 X "051, 

 •181 X "042 mm.), with simple, not very numerous warts, which may be arranged so as 

 to point towards the ends of the spindle. The cluhs (-187 X "051, -204 X '042 mm.) have 

 projecting warts, which may be either abruptly truncated or slightly toothed. There 

 are also small double clubs and irregular compact forms (-051 X "034, -058 X "025, 

 •034 X -17 mm.). 



Locality. Providence, 6 fms. 



Genus WRIGHTELLA. 



Note on the Genus. 



The series of Melitodes-like genera to which Gray's Wrightella belongs presents 

 many difficulties, especially because of the great variability of some of the species, as 

 Prof. Hickson has so well shown in the case of Melitodes variabilis, Hickson. 



If we retain Wrightella as a distinct genus, nearly related to Melitodes, it must be 

 more sharply defined. Towards this end we would point out that Wrightella is 

 characterised by distinctive spicules — short clubs with very broad flanges. The heads 

 of these clubs form a compact pavement in the coenenchyma, producing an almost roe- 

 like appearance, as in species of Bebryce. This is so characteristic that it is easy to 

 distinguish with the lens between a Wrightella and a Melitodes, which is the more 

 usef al since the convergence between these is extraordinarily close, as may be inferred 

 from our figures of Wrightella coccinea and Melitodes coccinea (Plate 13. figs. 4 & 7). 

 That these two forms, which seem identical to the unaided eye, are really quite different 

 will be admitted, we think, when our figures of the two sets of spicules are compared. 



Another point is that in spite of many trials of many specimens of Wrightella we 

 have not been able to find any longitudinal canal in the axis, though there is often a 

 hint of a softer core. 



