SPONGES — WHITELEGGE. 481 



5 to 10 mm. The frond-like expansion exhibits a series of lobes 

 and incisions; the former probably indicate the terminal branches 

 of the Gorgonia. 



On the basal portion of the sponge the surface is somewhat 

 smooth, with numerous minute pores and a few larger scattered 

 ones which vary from 0'5 to 1 mm. or more in diameter. The 

 upper four-fifths of the surface is ornamented with an immense 

 number of circular or subcircular pores from 5 to 3 mm. wide ; 

 the pores are seated, as a rule, in well marked grooves and 

 frequently in pairs. The intervening ridges are subradiate, and 

 may be narrow and continuous or occasionally broad and some- 

 what interrupted by a series of apical pores. Here and there a 

 few oscula-like openings are present, but they are very irregular 

 and appear like the borings of the common Isopod Cymodoce. 

 Size of apertures 3-5 mm. Texture hard and rather brittle. 

 Colour yellowish-white, with a slight sheen on the more perfect 

 dermal surface. 



Skeleton stellately reticulate, with the blunt ends of the spicules 

 overlapping and forming peculiar nodes like the knots in net- 

 work. The mesh is more or less triangular in consequence of the 

 star-like arrangement of the spicules. There is no evident spongin 

 present ; at least it is quite transparent and undistinguishable 

 with the microscope.* 



Megascleres : — straight or but little curved styli wholly spined 

 to within one diameter of the summit ; the latter is smooth and 

 usually very acute. Size about 0-2 to 0'22 mm. by O'Ol to 0-04 

 mm. Fusiform smooth oxea confined to the ectosome and rather 

 scarce. Size 0-18 mm. by 0'07 to 0'08 mm. 



Microscleres : — sigmata 0-05 mm., both simple and contort. 

 Tridentate isochelte 0*025 mm. Both kinds of microsclera are 

 fairly abundant in the membranes surrounding the pores. 



DENDORYX PUSCA, sp. nov. 



(Plate xlv., fig. 20.) 



Station 44. 



Sponge either massive or consisting of a series of short branches 

 which are often coalescent and form a tangled mass of branchlets; 

 the whole surface is minutely honeycombed, the trabeculse are 

 interwoven and the apical margins are minutely conulate. The 

 depressions are furnished with deep oval or round pores, from 



* See Bowerbank's figure of Diplodemia vesicicla, Mon. Brit, Spongidse, i., 

 1864, fig, 273. 



