8P0NGIIDA. 615 



near centre to sharp points ; size -32 by -0063 millim. (in axis of 

 outer extremities of primary fibres, and loose in the meshes of the 

 skeleton). ( I ) Tricurvate acerato, smooth ; the curves bold; ta] 

 ing to sharp points ; size -076 to -12 by '0032 millim. (in sarcodc). 

 (5) Equianchorato, shuttle-shaped, shaft slender, slightly and gra- 

 dually curved, palms each about one third the total length of the 

 spicule : length -025 millim. 



I l"l>. Marie Louise Island, Amirante group, 1 7 t'ms. : bottom coral. 



The specimen on which this species is based coats continuously 

 for a distance of 100 millim. (4 inches) most of the circumference 

 of a stem (probably algal) 3 millim. in thickness. The surface 

 of Spongia vulpina, Lamarck, in the Museum at the Jardin des 

 Plantcs, Paris, decidedly recalls this sponge; but that species is 

 tall, stipitate, and arborescent, with a superficial spicular incrustation, 

 and hence is rather referable to RTiaphidophlus than Clathria; it 

 seems to want the tricurvate acerate spicule of the present species. 



One remarkable point about the species is the unusually great 

 proportion of horny matter to spicules in the fibres. This is also 

 shown in Tenacia clathrata, Schmidt, of the W. Indies, which, besides 

 its clathrous habit, differs from this species mainly in the very coarse 

 horny fibre, the considerably superior dimensions of the smooth 

 acuates, and the rather clumsy form of the spined echinating 

 spicules. 



37. Acarnns ternatus. 



See Part L, p. 453, of this Eeport. 



A young specimen. The tricurvates are somewhat shorter, 

 thicker, and more strongly curved than in the Australian specimens. 

 Hah. lie des Neufs, Amirante Islands, 15 fms. 



ECHIN0NEMA, Carter. 



This genus was nominally established in 1875 (Ann. & Mag. jST. H. 

 1875, xvi. p. 185), in Mr. Carter's " Notes Introductory to the Study 

 and Classification of the Spongida," by the insertion of the words 

 " Echinonema typicum, C, MS.," under the Group Pluriformia, 

 Family Eetyonida, of the Order Echinonemata; but its characters were 

 not made known until 1881 (op. cit. 1881, vii. pp. 378-380;, when 

 Mr. Carter somewhat briefly described two species under this name, 

 viz. E. typicum and E. anchoratmn, without, however, giving any 

 definition of the genus. I have been able to examine a consider- 

 able number of the specimens thus identified by Mr. Carter, and find 

 them to be nearly allied to Rhaphidophlios of Ehlers (Espersch. 

 Spong. pp. 19,31) and to Clathria, Schmidt, having the same general 

 character of spiculation and arrangement of the skeleton as these 

 genera, but differing from Clathria in having a non-fibrous and 

 purely spicular cortical layer, composed of acuates or spinulates 

 with their points directed outwards, and while agreeing with 

 Bhaphidophlus in this point, differing from it in the possession (not 



