46 Mr. W. J. Sollas on a new 



at one end, seldom inflated, sharply pointed at the other 

 (PI. VI. fig. 6 and PI. VII. fig. 28) ; rounded end smooth, some- 

 times sparsely rnicrospined (PI. VII. fig. 27), O015 inch long, 

 0*0004 inch broad ; arranged matted together felt-like, sup- 

 ported on the ends of the large intermediate acuates, about 

 which they sometimes accumulate in a tent-like projection 

 (PI. VI. fig. 2). 



Sarcode. Flesh-spicules of two kinds, both very minute, 

 not exceeding 0'0003 inch in length — one a tricurvate (PL VI. 

 fig. 7 and PI. VII. fig. 19, b), the other an equianchorate, with 

 a straight or curved shaft and three recurved minute arms at 

 each end (PI. VI. fig. 7 and PI. VII. fig. 19, a), dispersed 

 through bright yellow sarcode. 



Hob. Marine. 



Loc. West Africa, lat. 15° S. 



Coll. Bristol Museum, presented by John Thwaites, Esq 



Obs. The single specimen of this sponge is in a very per- 

 fect state of preservation, having been well dried without 

 losing its sarcode. How it was obtained by Mr. Thwaites, 

 and from what depth in the sea, there is nothing to show ; but 

 its occurrence on the western side of Africa so far south as 

 15° from the equator is interesting, since both Oscar Schmidt's* 

 species of Plocamia came from the other side of the Atlantic 

 and north of the equator, viz. one from Florida at a depth of 

 195 fathoms (P. gymnazusa) , and the other from Cuba at a 

 depth of 270 fathoms (P. clopetaria). 



It is clear from O. Schmidt's definition of the genus Plo- 

 camia that our form must be referred to it ; and this reference 

 is made all the more certain by the close general agreement 

 between P. plena and the two previously described species, 

 both in structure and spiculation. In P. gymnazusa, O. S., 

 there is a large acuate in the intermediate layer, like that of 

 P. plena ; but our spined echinating acuate is represented by 

 a smooth form without spines • the needle-like spicules of the 

 dermis appear to be present in both, as well as the dumbbell- 

 headed, handle-like spicules of the axis. O. Schmidt does 

 not make any mention of flesh-spicules ; but as in P. plena 

 these are very minute, it is just possible that, if present in the 

 other forms, they may have escaped his attention. 



Putting these on one side, then, the distinction between P. 

 gymnazusa and P. plena, so far as it can be learned from de- 

 scription merely, appears to lie chiefly in the different form of 

 the echinating acuates : — in the latter a richly spined, straight, 

 or curved acuate with an inflated head ; in the former a smooth, 



* Grundzuge eiuer Spongienfauna des atlantischen Gebietes, pp. 62, 

 80, Taf. iv. figs. 17, 18. 



