770 MR. A. G, THACKER ON [June 16, 



developed peristome. There is also never an oscular fringe of 

 spicules in S. caminatum, a structure which is often present in 

 S. helleri. S. ccmiinatum is further distinguished by the presence 

 of more than one kind of oxea at the distal ends of the radial 

 chambers, by the absence from the radial chambers of sagittal 

 triradiates with the concave curves of their paired rays turned 

 towards the basal rays, and lastly by the merely sporadic occur- 

 rence of quadriradiates in the tubar skeleton, these spicules being 

 numerous in that region in ^S*. helleri. 



Distribution. Cape Verde Islands {Crossland Collection). 



Grasttia intermedia, sp. n. (Plate XL. fig. 5 & text-fig. 162.) 



Mr. Crossland collected a single specimen of this interesting 

 new species. This is an egg-shaped sponge (Plate XL. fig. 5) 

 6 mm. high and 5 mm. broad. The oviter surface is coarsely 

 hispid, large oxeote spicules projecting in every direction, and 

 there is a conspicuous osculum at the top (diameter 1 mm.) with 

 a well-developed oscular fringe, 1*5 mm. high. The specimen 

 was dredged from a depth of 20 fathoms off IsTorth Point, Boa 

 Yista Island. Its colour (in alcohol) is pale brown. The dermal 

 cortex is 0*16 mm. thick, the chamber-layer is 1*4 mm. thick, and 

 there is a feebly developed gastral cortex, making the total thick- 

 ness of the body -wall abovit 1*6 mm. The diameter of the gastral 

 cavity (at its widest part) is 1*7 mm. 



The specimen is not sufficiently well preserved to enable one to 

 make out the structure of the canal-system in any very great 

 detail ; but the exhalent canals are well developed, and the 

 chambers are very much branched. The canal-system is really 

 intermediate between the form typical of the genus Graniia on 

 the one hand and that of the genus Leucmidra on the other ; 

 in short, it is of the " sylleibid " type. The tubar skeleton is, 

 however, articulate and only shows slight signs of becoming 

 scattered, and for this reason I place the species in Gi^antia, not 

 in Leucandra. 



The Skeleton consists of all three forms of spicules. 



The tubar skeleton is composed of both triradiates and quadri- 

 radiates. The former are very variable in shape and are usually 

 very irregular. Their rays are sometimes straight, sometimes 

 curved, and all three angles are frequently unequal (text-fig. 

 162, a). The rays vary in length from 0'12 mm. to 0"24 mm. 

 and in thickness from 0*011 mm. to 0*014 mm. Some of the 

 triradiates in the tubar skeleton show a strong tendency to become 

 sagittal, and it is the basal rays of these that attain the greatest 

 length. There are a few, but only a very few, quadriradiates in 

 the tubar skeleton ; the apical rays of these are the same thick- 

 ness as, but shorter than, the facial rays and are cvirved at their 

 extremities. The facial rays resemble the rays of the triradiates. 

 None of the rays of either triradiate or quadriradiate spicules is 

 very sharply pointed. 



The dermal cortex consists of a compact mass of spicules resem- 

 bling those of the tubar skeleton ; the vast majority of the spicules 



