REPORT ON THE KERATOSA. 23 



as to whether it is really a sponge. Flemming^ and F. E. Schulze ^ have expressed such 

 doubts ; and Marshall^ feels more inclined to regard it as an alga than a sponge. Amongst 

 the Challenger specimens I find two forms which are well-marked representatives of the 

 species lanthella jlahellifortnis, and which are also distinct sponges with the canal system 

 after the type of that of Aplysilla or Dai-winella. The genus lanthella, like Darwinella, 

 is indeed a very good one, its chief generic character, viz., the presence of true cells 

 between the horny laminae of the skeletal fibres, being of an absolute nature, but it must 

 be added that with respect to the conjectural family Darwinellidse, this genus narrows the 

 diagnosis of the family as given by Vosmaer (On Velinea gracilis, p. 477), the skeleton of 

 its representatives being represented by fibres anastomosing with one another. 



Family Spongelid.b. 



In the family Spongelidse (I retain this name since the only one having the priority 

 over it is derived from the still doubtful genus Dysidea) six genera have been hitherto 

 distinguished, namely : — 



Velinea. 



We owe this curious genus to Dr. Vosmaer,* who places it in his family of Sponge- 

 lidoe, notwithstanding that its skeletal fibres are, at least in many instances, obviously 

 heterogeneous, but in accordance with its skeleton being represented by a network of 

 anastomosing fibres ; his Aplysillidje, on the other hand, being characterised by a 

 skeleton of tree-like shape. We have, however, learned that this latter character is 

 not admissible. The skeleton of lanthella is composed of anastomosing fibres, yet these 

 latter are heterogeneous, and the whole internal organisation constructed upon the type 

 of true Darwinellida3. The fact is that Velinea is a connecting link between this latter 

 family and Spongelidse, and as such it is indeed a very interesting form, but, as an inde- 

 pendent genus, belongs to those which from a systematic point of view are very ambiguous. 



S'pongelia, Dysidea, Psammascus. 



In the year 1834 Nardo^ subdivided his previous genus Aplysina into two subgenera, 

 " AplysincB velatice" and" AplysimB spongelioi." In the year 1842 Johnston^ created 

 the genus Dysidea for his Dysidea fragilis, which, according both to 0. Schmidt ' and 



' hoc. cit., p. 6. 2 Zeitschr.f. iviss. Zool, Bd. xxx. p. 381. ^ Jahresb. d. zool. Stat. Neapel, 1881, p. 161. 



* Mittheil. zool. Stat. Neapel, B.l. iv. Heft. 4, p. 437. ^ /jij.^ 1334, p. 714. 



" British Sponges, &e., p. 185. ^ Spoiig.-Fauiia des atlantiscli. Gebietes, p. 27. 



