APPENDIX — SPONGES OF THE "ARGO" CRUISE. 219 



Suberites ficus, Esper. 



Two specimens were dredged off Killybegs, August 10th, 

 at depths of 5 — 15 fathoms. 

 Aplysilla rubra, Hanitsch (PL XII, figs. 1-6.) 



HaUsarca rubra, Hn., Trans. L'pool Biol. Soc, vol. iv., p. 196, pi. x. 



The doubts which I expressed in regard to the 

 systematic position of this form, when describing it for 

 the first time, were not unfounded. The examination of 

 additional and well-preserved material has convinced me 

 that I must remove this sponge from the genus HaUsarca 

 to Aplysilla, a genus of the true Ceratosa. The skeleton 

 of Aplysilla, Schulze, consists, according to Lendenfeld,+ 

 of " numerous, isolated, small, dendritically ramifying, 

 upright fibres." In young specimens these fibres are 

 simple, not branching, and arise about at right angles from 

 the limiting membrane. I had noticed these fibres when 

 describing the sponge in my " Third Eeport on the Porifera 

 of the L.M.B.C. district," but I thought them to be hairs 

 of Mytilus, on which the sponge was found encrusting. 

 But the fact that the material dredged on the " Argo " 

 expedition was encrusting a stone, and a more careful 

 perusal of literature, have shown me that the fibres are 

 essential parts of the sponge. 



The specimen formed a small dark blood-red patch (3 

 mm. in diameter, 0'6 mm. in thickness) on the piece of 

 rock dredged off Arran Islands. Its surface is raised into 

 numerous sharp -pointed prominences, caused by the erect 

 spongin-fibres projecting through and dragging upwards 

 the neighbouring parts of the dermal membrane and other 

 tissues. These fibres are isolated and simple, and spring 

 about at right angles from the limiting membrane. Their 

 diameter in the centre of the sponge is O007 mm. We 



* R. v. Lendenfeld, "A Monograph of the Horny Sponges, p. 698. 



