BRITISH SPONGIAD.E. 255 



The tension spicula of this species present valuable dif- 

 ferential characters, their sub-clavate or hastate termination, 

 readily distinguish this species from the nearly allied ones 

 of H. i?icrasta?is and II Batei, in the tension spicula of 

 which species, these peculiarities of termination never occur. 



18. Halichondria Pattersoni, Boiverbank. 



Sponge. Coating (?) ; surface smooth, minutely corru- 

 gated. Oscula simple, dispersed. Pores inconspi- 

 cuous. Dermal membrane pellucid, abundantly spi- 

 culous; spicula cylindrical, incipiently terminally 

 spined, fasciculated loosely and irregularly. Skeleton 

 spicula acuate, entirely spined, rather stout. Reten- 

 tive spicula angulated, dentato-palmate inequi-ancho- 

 rate; distal palm about half the length of the spi- 

 culum, solitary and very few in number. 



Colour. Nut-brown in the dried state. 

 Habitat. Strangford Lough, Professor Dickie. 

 Examined. In the dried state. 



I am indebted to my friend Professor Dickie, of Aber- 

 deen, for my knowledge of this species. I received from 

 him four fragments, the largest of which was nine lines in 

 length by four in breadth, and about one line in thickness, 

 and there is every appearance of its having coated a flat 

 and even surface. A few fragments only of the dermal 

 membrane were left upon the sponge, but the positions of 

 the oscula were distinctly indicated by the terminations of 

 the excurrent canals at the surface of the sponge. The 

 spicula of the skeleton are similar in form and spination to 

 those of H. incrustans and //. Dichei, but they are smaller 

 by about one fourth of the length of the latter ; but the 

 essential difference from the above-named two species exists 

 in the incipient spination of the termination of the tension 

 spicula, which are distinctly seen with a power of about 

 300 linear, and in the form of the anchorate retentive 

 spicula, which are very few in number, and which can only 



