42 THE VOYAGE OF H.M.S. CHALLENGER. 



Grantia tuberosa, n. sp. (PL I. fig. 6; PL III. figs. 6-13). 



This Sponge differs from all other species of the genus by its large acerate spicules, 

 which sometimes stand perpendicularly to the surface of the Sponge, but usually turn 

 down into the parenchyma, not only piercing it in an oblique direction, but also — and this 

 is very often the case — lying parallel to the outer surface, and thus either perpendicularly 

 to the longitudinal axis of the Sponge, or parallel to it, or formingjwith it a more or less acute 

 angle. This is a very interesting fact, for it indicates how a cortex of acerate spicules 

 longitudinally disposed, — the chief character of the genus Ute — might have taken origin. 



The species is represented in the Challenger collection by a complete specimen and 

 some fragments. The first is of tubular form with extended base, 15 mm. long and 

 6 mm. broad in the middle ; the thickness of the walls reaches 1 mm., the diameter of 

 the osculum 2"25 mm. On one side of the outer surface are to be seen two nodular pro- 

 minences, perpendicular to the longitudinal axis of the Sponge — probably incompletely 

 developed gemmae. Such a transverse gemmation has been also observed in Amphoriscus 

 stauridia (Hseckel 1 ). The outer surface is smooth, the inner surface slightly roughened 

 by the apical rays of the gastric quadriradiate spicules. The radial tubes are irregular 

 in their outlines, and show a tendency to ramify ; the tubar pores are in this species 

 larger and more numerous than I have ever seen them ; the disposition of the tubar 

 spicules is not so regular as is usually the case in the tubes with articulated skeleton. 



Skeleton. — The skeleton consists of gastric quadriradiate, of subgastric triradiate or 

 quadriradiate, of tubar triradiate, of large acerate, of minute cortical acerate, and of cortical 

 sagittal and irregular triradiate spicules. 



Gastric quadriradiate spicules. — All the rays of the same diameter (O012 mm.), tapering from 

 the base to sharp points ; basal ray straight, often rather shorter than lateral rays, these 

 latter being on an average - 3 mm. long; lateral rays smooth, either straight or slightly 

 curved, forming with basal ray an angle of about 115°; apical ray curved, rarely longer 

 than O08 mm. 



Subgastric triradiate spicules. — All the rays of the same diameter (0 - 02 mm.); basal ray straight, 

 tapering from the base to a sharp point, reaching 0'38 mm. in length, forming with each 

 of the lateral rays an angle of about 110°; lateral rays sharp-pointed, curved, often 

 undulating, either lying in the same plane with basal ray or forming with one another an 

 angle varying from 180° to 165°. Many of the subgastric triradiate spicules are provided 

 with embryonal fourth rays, occasionally reaching O04 mm. in length, but half as thick as 

 the other rays. 



Tuhar triradiate spicules. — All the rays sharp-pointed, of the same diameter (O02 mm.), lying 

 in the same plane ; basal ray straight, its length varying from 0*12 to 028 mm. ; lateral 

 rays curved outwards, often undulating, 025 mm. long, each forming with basal ray an 

 angle varying from 112° to 130°. 



1 KaLkschwamme, Bd. ii. p. 246. 



