1908.] CAPE VERDE ISLANDS SPONGES. 773 



much in size ; the average length of their I'ays is 0"3 mm. and 

 the thickness at base is 0*04 mm. 



The skeleton of the dermal cortex consists of three kinds of 

 spicules : — (1) Regular or sub-reg\dar triradiates similar to those 

 of the chamber-layer but smaller ; average size 0'2 x 0'025 mm. 

 (2) Sagittal tiiradiates : basal ray pointing towards the base of the 

 sponge ; these vary up to a maximum size of — paired rays 0"3 x 

 0'04 mm., basal ray 0*2 x 0'04 mm. ; the basal ray is always 

 shorter than the other two. (3) Sagittal quadriradiates, similar 

 to the sagittal triradiates except for the presence of a straight 

 apical ray, about one quarter the length of and three quarters the 

 thickness of the paired rays ; these spicules do not appear to reach 

 such a large size as the sagittal triradiates. 



The gastral cortex consists of small quadriradiates and tri- 

 radiates ; the former are mostly sagittal with curved paired rays, 

 a long straight basal ray, and a rather short curved apical ray 

 (text-fig. 163, d). The length of the paired rays in these 

 spicules is on the average 0"15 mm. and the width O'OIS mm. ; 

 the basal ray is rather longer and the size of the apical ray is 

 0'05 X 0'009 mm. The quadriradiates are sometimes irregular, 

 sometimes nearly regular in shape, but they vary very little in size. 

 The triradiates (text-fig. 163, e) of the gastral cortex also vary 

 in shape, but are usually rather irregular ; the average size of 

 their rays is 0"15x0'015 mm. 



jDist7'ibution. Cape Verde Islands {Crossland Collection). 



Leucandra rudifera (Polejaeff). (Plate XL. fig. 7 & text-fig. 

 164.) 

 Synonymy : — 



LeuGonia rudifera Polejaeff [19]. 



A few fragments of this species, which is characterised by the 

 possession of very peculiar minute oxeote spicules in the gastral 

 cortex, were collected off Bermuda by the ' Challenger ' and were 

 described by Polejaeff. Mr. Crossland dredged three specimens, 

 all of which are complete, so that I am foi-tunately able to add 

 the description of the external foi-m to that of the skeleton which 

 was given by Polejaeff. 



The sponge (Plate XL. fig. 7) is composed of an irregularly 

 massive bulbous Leucon individual, and in the largest specimen 

 reaches a height of 2 cm. and a maximum width of 1'7 mm. The 

 smallest specimen is egg-shaped ; no doubt this is the young form 

 and the irregularly massive appearance is acquired with growth. 

 There is a large circular osculum at the top ; there is a peristome, 

 and two of the specimens possess oscular crowns. The thickness 

 of the body-wall varies very much : in the lai'gest specimen it is 

 as thick as 8 mm. in one place and as thin as 2 mm. 'w\ another. 

 The maximum diameter of the central gastral cavity is 6 mm. 

 The external surface is only slightly hispid, for the large oxea 

 either do not project at all or project only slightly. The internal 

 surface is rough owing to the projection of the apical rays of the 

 gastral quadriradiates. 



