3G8 'S\v. TI. .1. Carter on the ITcxactinelliJiv, 



of the Atlantic Ocean, probably somewhere between the west 

 coast of Ireland and the Fiiroe Islands ; so that it seems reason- 

 able to infer that when there is a tuft of long anchoring-spicules 

 present it is indicative that the Euj^Jectella has grown in 

 mud — and when absent, that it has grown upon some hard 

 object. 



Alcyoncelhmi speciosum and A. corhicula appear to me to 

 belong to one and the same species ; and when we find Prof. 

 Thomson, who examined them carefully and got photographs 

 made of them, stating respecting their differences, " I am not 

 quite satisfied on this point even now" ('Annals,' I. c. p. 129), 

 one wonders that he made any difference in their designation. 



As regards size, E. aspergillum^ E. cucumer^ and Hahro- 

 dictyon are almost all equal : . hence it cannot be assumed that 

 either is a young form of the other ; and while it may reason- 

 ably be inferred that the two specimens of AUyoncelliim might 

 reproduce each other, it by no means appears likely that either 

 of the three species above differentiated could do this. 



Hence, although in general fonn all three are alike and all 

 possess the characteristic rosettes of Euplectdla (PL XIII. 

 figs. 4 & 11, a, J), yet between these two extremes there are 

 the differences above mentioned, together Avith many other 

 minor ones, which indicate that they are three distinct species. 



Here I would take the opportunity of mentioning that Mr. 

 Kitton, of Norwich, informs me that he possesses a specimen 

 oiEuphctella aspergillum in which there is a netted diaphragm 

 — which is so far interesting as it still more nearly allies the 

 structure of this sponge to that of the Aphrocallistidas, where the 

 diaphragm is a normal and constant occuiTcnce. 



As Apkrocallistes, Farrea, and Aidodictyon will be parti- 

 cularly described in the after part of this paper I shall say 

 nothing more of them here. 



In SympageUa mix, Sdt., there is the same ladder-like vitri- 

 fied fibre as in Euplectella, but not the form of the rosette 

 peculiar to the latter. Of the two forms of rosette, one is the 

 common one (PL XIII. fig. 6), and the other the pappus-like or 

 pappiforra rosette with flexed rays, no heads, and arranged en 

 fieur-de-lis (figs. 12 & 15), noticed in one other genus only, 

 viz. Rossella. The ladder-like fibre is well illustrated by 

 Schmidt (Atlantisch. Spongienf. Taf. i. figs. 9-12). 



We come now to the sarcospicidous Hexactinellida?, or those 

 whose spicules are held together by ?mvitrified sarcode, of 

 which the first is Ashonema setuhalense. 



Of this sponge, as I have had nothing for examination but 

 a fragment brought from Lisbjn to the British Museum by 



