Sponjes from the Atlantic Ocean. 395 



Ilah. Marine, growing erect in a sandy hottoni, in whicli 

 the root-like fibros arc spread ont for lixafJDn. 



Lor. Cliii'lly between the nortli of" Seotland and the Fiiroc 

 Islands. 



Ubs. The above deseription shows that the strneture of the 

 head is essentially like that of the sessile PolymastiiP,^ ]5k. ; 

 hence its desii:;nation ; while the lower end of the stem, being 

 suddenly enlarL!;ed and terminating in a bunch of mnnerous 

 rooth'ts, contrasts strongly with the tollowijig species, which is 

 the reverse, although the structure of the head here too will 

 be seen to resemble that of Polymastia. At first I thought 

 Polymastia stij)itata was Sars's llyalonema longissimian, since 

 some of the specimens of the former (which came from near 

 Cape 8t. Vincent) are exactly like his figures: but tiicre is no 

 central inflation of the spicule in any of them ; and if there 

 were, there would be no sexradiate cross of the central canal, 

 whicli is peculiarly, as Schmidt has noticed, the character of 

 the liexactinellida : therefore I wonder that the name of 

 " Hyalonema " should have been applied to these sponges ; a 

 glass stem alone does not make a hexactinellid sponge. The 

 same might be said of Lovc'n's //. horeale (figs. 9-11, '■ Ann.' 

 18G8, vol. ii. p. 81, pi. vi.) ; while Prof. Wy. Thomson 

 (' Depths of the Sea,' p. 114) only gives a figure of the entire 

 sponge without alluding to the form of the spicules. Still 

 the forms reprcscntal by Lovdn's, Sars's, and Thomson's 

 figures respectively of the entire sponge are all present among 

 those dredged up on board the ' Porcupine,' none of which 

 have any central inflation on the spicule : or if so, it must 

 be the exception ; for after repeated examinations 1 have not 

 found one. 



Cometella simplex^ n. sp. (PL XVI. fig. 53.) 

 General form consisting of a head and stem. Head obovate 

 globular, passing below into a fine stalk, which, narrowing 

 towards the lower end, divides dichotoraously into a few deli- 

 cate, dendriform, root-like fibres. Colour light yellow. Sur- 

 face of head and stem hirsute throughout, hirsuteness espe- 

 cially prominent over the former, arising from the jirojection 

 of the pointed ends of the spicules. Pores and vents not evi- 

 dent. Internal structure radiate, consisting of bundles of large 

 spicules extending from a central })oint to the circumference, 

 where they are met by a much smaller set, which together pro- 

 duce the hirsute appearance; hciid in a longitudinal section pre- 

 senting a thin transparent dermal layer, then an opaque much 

 thicker subdermal zone, followed by a layer of compressed 

 cavities, which belong to the e.vcretory canal-system, finally 



97* 



