510 Mr. H. J. Carter on 



In the next species that will be described, viz. Clathrina 

 priinordialis, the reticulated flat lamina of C. laminoclathrata 

 appears to be replaced by a vermiculated tube, in which the walls 

 are just as thin as the lamina of this species, but which tubula- 

 tion by repeated branching, contortion, and anastomosis, all 

 more or less in apposition, assumes the form of a solid mass of 

 this kind of structure in which the intervals between the tubu- 

 lation afford a much larger space for parenchymatous structure 

 than in C. laminoclathrata ; in short, wherein the quantity 

 of parenchymatous structure is much greater. 



6. Clathrina primordialis. 



(See Ascetta primordialis, H. o/j. cit. Atlas, Taf. ii. fig. 13.) 



A massive, shapeless, sessile, sublobate, smooth, solid lump, 

 attached by a plurality of portions of the body elongated into 

 podal points below, whose interspaces extend upwards in an 

 irregularly excavated manner towards the surface, where the 

 lobes of the mass terminate in thick, irregularly interuniting, 

 round, submeandering ridges, with intervening depressions, 

 some of which extend down to the interspaces between the 

 points of attachment ; ridges on a level with each other, 

 forming the crown of the mass. Texture delicate, light as 

 cork when dry. Colour when fresh not given, probably 

 whitish, as in one of the specimens, but now more or less 

 pinkish brown, probably, as before stated of Clathrina tri- 

 podifh-a, from having been in the proximity of a similarly 

 coloured sponge. Surface minutely ridged, quasi fibro-reti- 

 culately, with more or less lozenge-shaped interstices, smooth, 

 even, covered throughout with an epithelial layer of cells 

 more or less transfixed by the rays of subjacent spicules. 

 Pores in the quasi fibrous ridges. Vents of two sizes, viz. 

 small and large, both z/?anarginated and on a level with 

 the surface, viz. : — 1, smaller, circular, numerous, in the 

 interstices of the fibro-reticulated ridges, averaging l-48th in. 

 in diameter, and about the same distance a])art; 2, larger, 

 also circular, but flabby and comparatively scanty, scattered 

 irregularly among the rest, chiefly over the projecting 

 portions of the crown. Structure tortuously tubular, the 

 tubes composed of a single layer of triradiates, held together 

 by sarcode, averaging about l-72nd of an inch in diameter, but 

 very irregular in their calibre, branched, anastomosing, and 

 in juxtaposition but for the presence of a narrow strip of 

 parenchymatous tissue, which here and there becomes widened 

 out into angular spaces, where the circular walls of the tubu- 

 lation fail to come in contact with each other. Ano;ular 



