222 MR. n. KIRKPATRICK ON THE PORIFERA [Mar. 6, 



arranged spicules. Spicules of two kinds, viz., thick, slightly 

 curved, sparsely spined strongyles and longer, more slender, 

 smooth strongyles. Gemmides ? 



Description. — Of the new species there are three small specimens 

 in the form of thin crusts, the largest of which is 26 x 11 rum. in 

 area and -S-'T mm in thickness. The crusts, which have been 

 separated from stones, still retain the curvature of the surfaces 

 on which they grew. Their consistence is flexible and elastic, so 

 that when they are pressed flat they immediately resume their 

 convexity when pressure is removed. 



The surface is uniformly level, and in tlie dried condition has a 

 glistening aspect, owing to the reflexion of the light from the 

 tangentially disposed dermal spicules. 



The oscules are neaily circular, and in the specimens quite level 

 with the surface ; but probably in the perfect condition each is 

 surrounded by a slightly raised membranous rim, since traces of 

 such a membrane still remain on one of the oscules. Each 

 oscule leads into a shallow basin, whence the main exhalant canals 

 radiate out horizontally. 



The skeleton forms a network in which main and secondary 

 fibres are not perceptible ; the meshes (about 95 ju in diameter) 

 are irregularly triangular and polygonal, the strands being from 

 2-3 spicules thick. 



The dermal skeleton (Plate XVI. fig. 2) forms a lattice- workwith 

 triangular meshes, with strands 1-2 spicules thick formed of 

 tangentially arranged spicules. Though the dermal layer is dis- 

 tinct, it is not easily separable from the parts beneath. 



At the base of the sponge is a well-defined lamella of spongin 

 (Plate XYI. fig. 4), whence arise thick horny fibres with a core of one 

 or more siliceous spicules ; the fibres attain a thickness of 38^. 

 A short distance above the basal plate the spongin disappears, 

 and the core of spicules is continued on into the general spicular 

 network. 



Spicules. — The strongyles with sparsely and finely gi'anulated 

 surface are 115-145/^ long and 5-6 ju broad, with the ends often, 

 but not always, slightly and gradually enlarged (Plate XVI. 

 fig. 5) ; occasionally also there is a central swelling. 



The longer and more slender strongyles, 150-170^ x 2*75 ju, 

 are smooth and taper towards the blunt rounded ends (Plate XVI. 

 fig. 6). 



There are no gemmules present in the specimens. 



Affinities. — Although there are no gemmules present, and the 

 megascleres are strongyles, I have placed the species in the 

 genus /SpoQigilla, rather than in TJimguaya {Potamolepis)^ because 

 its affinities seem to be with certain species of /Sjyooigilla, viz. 

 'S'. hohmii Hilgendorf *, S.nitens Carter, and ^S'. ^:'erm^a;to Weltner, 



* VosfMy Pota-Molepis toeltne}'!, Moore (' The Tanganyika Problem,' 1903, p. 323) 

 may be sj-uonymous with Spongilla bohmii. I find the shajje and size of many of 

 the strongyles of the skeletal framework to be absolutely identical in the two species. 

 Moore's figures (?. c. p. 323) of tlie spicules of P. loeltneri are not quite correct, in 



