SPONGES — VVHITELEGGE. 475^ 



The skeleton consists of wavy, radiating bundles of spicules 

 from 0-2 to 0-4 mm. in diameter. The main fibres are longitudi- 

 nally arranged and give off a series of secondaries which terminate 

 in whispy clusters near the surface. The areas of elevation are 

 surrounded by a vast number of spicules, which are disposed in a 

 radiate manner, and probably act like a valvular arrangement for 

 closing or opening the apical pore. 



The dermal membrane is supported by the radiating pillars of 

 spicules, and has many others irregularly scattered in the 

 choanosome. The epidermis is about 0-5mm. in thickness and is 

 densely packed with isochelse, many of which are in contact Avith, 

 or even overlap each other ; they are rarely more than their 

 length apart. 



Megascleres : — straight, smooth, slightly fusiform styli, with 

 acute points and a well rounded, but tapering base ; size, 0-6 to- 

 0'7 mm. long by 0-0065 to 007 mm. in diameter. 



Microscleres : — these consist of strongly bent isochelse, each end 

 with three subequal teeth ; they are extremely abundant in the 

 dermis, and either in tracts or scattered rather sparsely in the 

 choanosome ; size from 0-025 to 0-03 mm. This species differs in 

 many characters from the type of the genus, \iz., in habit, and 

 the larger spicules, which are quite smooth, without any tendency 

 to become polytylote. 



DESMACIDON, Boiverhank. 



DESMACIDON PORIFERA, sp. nov. 



(Plate xliii., fig. 5.) 



Stations 34, 44, 36. 



Sponge stipitate, much branched, and here and there coalescent. 

 The branching is mostly lateral, rarely dichotomous. Alain 

 peduncle 10 mm. in diameter and from 60 to 90 mm. in length ; it 

 exhibits numerous short, more or less prominent angles arranged 

 longitudinally. The branches are angular and subparallel, they 

 are from 5 to 8 mm. in diameter and from 90 to 200 mm. or more 

 in length ; at or near their origin they are abruptly curved 

 upwards. The surface generally is very porous, the pores varying 

 in size from 0-1 to 0'2 mm. in diameter. Oscula numerous, 

 prominent, and usually surmounting the angles on the peduncle 

 and branches. Their diameter varies from 1 to 2 mm., and they 

 are from 4 to 6 mm. apart. Skeleton composed of a rather open 

 reticulation of fibres ; the primaries traverse the central axial 

 region and give off" numerous secondaries, which curve outwards, 



