Sponges from the Atlantic Ocean. 395 



Hah. Marine, growing erect in a sandy bottom, in which 

 the root-like fibres are spread out for fixation. 



Loc. Chiefly between the north of Scotland and the Faroe 

 Islands. 



Ohs. The above description shows that the structure of the 

 head is essentially like that of the sessile Polymasticej Bk. ; 

 hence its designation ; while the lower end of the stem, being 

 suddenly enlarged and terminating in a bunch of numerous 

 rootlets, contrasts strongly with the following 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 stipitata was Sars's Ryalonema longissimum^ since 

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

 Cape St. Vincent) are exactly like his figures : but there 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, 

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

 tlie Hexactinellida : 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 Loven's H. horeole (figs. 9-11, ' Ann.' 

 1868, vol. ii. p. 81, pi. vi.) ; while Prof. Wy. Thomson 

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

 sponge without alluding to the form of the spicules. Still 

 the forms represented by Loven'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 I have not 

 found one. 



Cometella simplex, n. sp. (PI. XVL 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 dichotomously 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 projection 

 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 jDoint to the circumference, 

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

 duce the hirsute appearance; head 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, whicli belong to the excretory canal-system, finally 



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