54 TDK VOYAGE OF H.M.S. CHALLENGER. 



ol (rarely shorter) to Of, mm.; basal ray straight, tapering from the base to an approxi- 

 mately sharp point, forming with each of the lateral rays an angle of 105° to 110°; lateral 

 rays either straight or slightly curved inwards, sharp-pointed; apical ray straight, taper- 

 ing from the base to a sharp point, never projecting from the inner surface, length 

 varying from 0'4 to 1/2 mm. 

 Dermal acerate spicules.— Straight, fine, linear, sharp-pointed, surface smooth, length not 

 exceeding 04 mm., with a diameter of 0-0025 rum, ; not numerous ; projecting from the 

 outer surface. 



Colour. — White and yellowish. 



Habitat. — Station 36, April 23, 1873; off Bermudas; depth, 32 fathoms. Station 

 209, January 22, 1875 ; lat. 10° 10' N., long. 123° 55' E. ; Philippine Islands ; depth, 95 

 to 100 fathoms. 



Leuconia, Bowerbank. 

 Leuconidse with an irregular disposition of the spicules of the parenchyma through- 

 out ; with roundish flagellated chambers. 



Leuconia multiformis, n. sp. (PI. I. fig. 8; PI. II. fig. 1; PL VI. figs. 3a-3c; 

 PI. VII. figs, la-lh). 



There are in the Challenger collection more than fifteen specimens, which, however 

 different with regard to their external shape, are to be all referred to this species ; two 

 of the most typical representatives may be seen drawn in their natural size on PI. I. 

 fig. 8, and PI. II. fig. 1. The chief character distinguishing this form from all the species 

 of Leuconia hitherto known — so far at least as the existing descriptions permit us to 

 form a judgment — is to be found in its subgastric triradiate spicules, which are of the 

 same shape as those in Amphoriscus and Leucilla. It is for the last time that we meet 

 with this interesting shape, and here in Leuconia multiformis they are in most cases 

 so slender, in comparison with other constituent parts of the skeleton of the paren- 

 chyma, that their phylogenetic signification seems to be beyond all doubt. At any 

 rate, together with peculiarities in form and size of other spicules of the skeleton, they 

 present a character allowing of a distinct definition of the species. 



According to the greater or less predominance of the large acerate, and to the presence 

 or absence of minute acerate spicules, I subdivide the species into three varieties with 

 the following diagnoses : — 



Leuconia multiformis, var. yoliaih. 



Outer surface naked, acerate spicules either not projecting at all from the cortex or 

 standing isolated at greater or less distances from one another. On the gastric surface 

 triradiate spicules more numerous than quadriradiate. 



