1908.] 



CAPE VERDE ISLANDS SPONGES. 



771 



are triradiate, but there are a few quadrii'adiates as well. Both 

 triradiates and quadriradiates are sometimes sagittal, and in this 

 case they have their basal rays pointing towards the base of the 

 sponge, as is usual in the genus. 



The gastral cortex is 0"07 mm. thick, and is composed of tri- 

 radiate and quadriradiate spicules similar to those occurring in 

 the tubar and dermal cortical skeleton, but in this portion of the 

 sponge the quadriradiates form a much lai-ger pei-centage of the 

 whole number of spicules than they do in the tubar skeleton or 

 dermal cortex. The apical rays of the quadriradiates project into 

 the gastral cavity. There are sagittal triradiates and sagittal 

 quadriradiates with basal rays pointing towards the base of the 

 sponge. 



Text-fig. 162. 



Spicules from Grrantia intermedia. 

 a = Triradiates X 120. b = Quadriradiates X 120. c = Oseotes X 24. 



There are also some " sub-gastral sagittal triradiates," viz., 

 triradiates just buried within the gastral cortex and having a 

 basal ray pointing horizontally outwards towards the dermal 

 surface — in the same direction as the basal rays of the irregularly 

 sagittal triradiates of the tubar skeleton point ; the sagittal tri- 

 radiates in this position closely resemble the sagittal triradiates 

 in other situations. 



There are some enormous oxeote spicules projecting from the 

 surface of the sponge. These are not arranged in groups, but 

 emerge from the surface without definite order and either at right 

 angles to the surface or more or less obliquely. Their proximal 

 ends are buried more or less deeply in the tubar layer of the body- 

 wall. The spicules are spindle-shaped, are rather bluntly pointed 

 at both ends, reach a length of 2 mm., and have a maximum 

 thickness of 0*06 mm. (text-fig. 162, c). 



The oscular fringe is composed of very long and very fine oxeote 

 spicules. These reach a length of 3 mm. and have a maximum 

 thickness of 0*008 mm. 



Distribution. Cape Yerde Islands {Crossland Collection). 



