222 MR. 11. KIRKPATRICK OX THE PORIFERA [Mar. 6, 



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

 curved, sparsely spined strongyles and longer, more slender, 

 smooth strongyles. Gemmules ? 



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

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

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

 separated from stones, still retain the curvatuie of the surfaces 

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

 that when they are })ressed flat they immediately resume their 

 convexity when pressure is removed. 



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

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

 tangentially disposed dermal spicules. 



The oscules are neai-ly 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 net^voi-k in which main and secondary 

 fibres are not perceptible ; the meshes (about 95 fx 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- work with 

 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 XVI. fig. 4), whence arise thick horny fibres with a core of one 

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

 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 spai'sely and finely granulated 

 surface are 1 15-145 |u long and 5-Q ft broad, with the ends often, 

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

 fig. 5) ; occasionally also there is a centi'al swelling. 



The longer and more slender strongyles, 150-170/.t x 2"75yu, 

 are smooth and taper towards the blunt i-ounded ends (Plate XVI. 

 fig. 6). 



There are no gemmules present in the specimens. 



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

 megascleres are sti'ongyles, I have placed the species in the 

 genus Spongilla, rather than in Uruguaya {Potamolepis)^ because 

 its affinities seem to be with certain species of Spongilla, viz, 

 /S'. hohmii Hilgendorf *, S.nitens Carter, and S.permixta Weltner, 



* Possibly Poi!(?TOo/epjs weltnerl Moore (' The Tanganyika Problem,' 1903, p. 323) 

 may be synonymous with Spoiifjilla bahmii. I find the sliai^e and size of many of 

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

 Moore's figures {J. c. p. 323) of the spicules of P. iveltneri are not cpiite correct, in 



