100 BRITISH SPONGIAD2B. 



16. HALICHONDRIA ROBERTSONI, Boiv., n. sp., TV, Plate V, 

 figs. 814. 



" Sponge massive, sessile. Surface smooth 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 ; basally 

 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 



