100 BRITISH SPONGIADiE. 



16. Halichondeia Robeetsoni, Bow., n. sp., tv, Plate V, 

 figs. 8—14. 



" Sponge massive, sessile. Surface smootli and even. 

 Oscula simple, dispersed. Pores inconspicuous. Dermal 

 membrane profusely spiculous ; spicula fasciculated ; 

 fasciculi broad and flat, irregularly disposed. Spicula 

 cylindrical, smooth, more or less hastate, or terminat- 

 ing acutely. Retentive spicula tridentate, equi-ancho- 

 rate, small, but stoutly proportioned, dentes expanded ; 

 and also bihamate, minute, and slender ; both forms 

 few in number. Skeleton symmetrical, rete bi- or tri- 

 spiculous ; spicula acuate, short and stout ; basaUy 

 and apically spinous, spines few in number. Inter- 

 stitial membranes spiculous, tension spicula long and 

 very slender, cylindrical, few in number; retentive 

 spicula same as those of the dermal membrane, few. 



" Colour. — In the dried state, nut brown. 



" Habitat. — Unknown. 



" Examined. — In the dried state. 



" The specimen in course of description was given by 

 the late Dr. Scouler to Mr. D. Robertson, and by him 

 to my friend the Rev. A. M. Norman, by whom it was 

 sent to me for examination and description. The late 

 Dr. Scouler, I am aware, was a collector of the sponges 

 of the Irish seas, and therefore I have no doubt of its 

 being a British species, although its locality is un- 

 known. 



" The sponge has apparently been seated on a solid 

 mass of rock, from which it has been removed by a 

 sharp instrument, and no portion of the basal mem- 

 brane remains on it. In its present condition its form 



