TETRAXONIDA. 11 



CiNACHYRA VERTEX var. moiiticularis. 

 (Plate X., figs. 15, 16. Plate XL, figs. 1-3.) 

 1907. Ginachyra vertex Lendenfeld (11a. p. 310). 



Two small specimens of this species, obtained from deep water (130 fms.), 

 show a remarkable variation in the porocalyces and oscules. The porocalyces instead 

 of being situated below the general surface are elevated above it in the form of 

 rounded warts or monticules about 1 mm. in height ; the oscules likewise form 

 small cylindrical chimneys about 2 mm. in height. 



The larger of the two specimens is 3" 5 x 2*5 cm. in its diameters, not including 

 the root-tuft, which is about 2 cm. in thickness. A large part of the surface is covered 

 with tlie little porocalycal monticules, and at one end are several oscular chimneys. 

 Situated at a varying height on each monticule is a semilunar slit which opens into 

 a ca3cal fold or pocket that has been formed by the upward growth and protrusion 

 of the monticule ; when the lip is near the summit of the monticule, it surrounds the 

 latter like a kind of prsepuce. The pore-perforated floor of the porocalyx itself is, 

 in every instance, closely folded with longitudinal pleats which, however, can be unfolded. 

 The summit of the monticule is formed by the tops of these folds, and liundles of tlie 

 hispidating trichodal protriaenes can occasionally be seen projecting from the summit. 

 The long slender l)undles of protriaenes divide into two layers at the inferior proximal 

 edge of the semilunar fold, one set being in the fold itself and extending to the edge 

 of the same and sometimes a little beyond, the other set passing up in to the floor and 

 walls of the porocalyx itself. The edge of the semilunar lip is provided with a Imnd 

 of myocytes. This curious variation appears to have taken place as an adaptation 

 necessitated by the spiral mode of growth of the sponge ; if such growth became 

 excessive the porocalyces would be in danger of becoming closed altogether from one 

 lip of the orifice overlaying the other. 



Locality. Winter Quarters. No. 10 Hole, 130 fms. 



II.— Grade MONAXONELLIDA, Dendy. 



There are, in all, forty-three species belonging to this group. Of these, eight 

 belong to the Astromonaxinellida, and thirty-five to the Sigmatomonaxinellida. 

 Twenty-two species are new, and there are, in addition, seven new varieties of species 

 already described. There are four new genera, of which one l)elongs to the Axinellidae, 

 two to the Mycnlinae, and a fourth, Pyloderma (Eeuierinae), has been established to 

 receive Halichondria latrunculioides Ridley and Dendy. 



New and Interesting forms of spicules. — The new Mycaline genus Cercidochda is 

 characterised by the possession of remarkable modified isochelae, which I have termed 

 canonchelae {i.e., shuttle-shaped chelae). In them the single central teeth from each 

 end have fused, so that a complete shuttle-shaped spicule results, recalling the melon- 



