Report on the zoological collections made in the Indo-Pacific Ocean ...

398 COLLECTIONS FROM MELANKSIA.here few in number and reduced in dimensions : the primary fibresare more slender and much more strongly spicular, and I have notobserved here the cylindrical form of spicule which accompanies theacerate in G. armigera ; the vents are more abundant and the growthis repent, instead of suberect. Still I believe the species to be notremotely allied ; and this near relation between two species, one ofwhich has an aculeated surface and an erect growth, while theother is decumbent and scarcely at all aculeated, shows how littlevalue for the group-distinction of the Chalinidfe such characters maypossess. The variation shown by different specimens (see description)is somewhat wide.26. Cladoclialiiia pergamentacea.Cladochalina armigera, var. pergamentacea *, Ridley, P. Z. S. 1881,p. 112, pi. X. %. 4.A young specimen of compressed form, smooth surface, and witha row of vents along each margin, with the fibre as in C. armigera,and spicules measuring "09 by -0016 millim. and shaped like thoseof C. armigera, seems to belong to the above form.Hah. Thursday Island, Torres Straits, 3-4 fms. (on Retepora).Distribution. Hotspur Bank, off S.E. Brazil (Hidley).ACERYOCHALINA, g. n.Chalina, Schmidt, Suppl. ii. Adr. Meer. p. 10 (iiec Botverbank').Massive, sessile Chalinidae. Fibre strongly ceratinous, containingaxially or diff'usely arranged slender acerate spicules, which do notexceed in bulk the horny material of the fibre which contains them.Vents distinct, ranged along upper surface.Type Chalina limbata, Bowerbank (Mou. Brit. Spong. ii. p. 373 ;? Montagu).This genus appears to be most closely allied to Cladochalina, byits strong relative development of keratose, its fine acerate spicules,and its serial vents. Mr. Carter indicated the distinctness of suchforms as long ago as 1875, when (Ann. & Mag. N. H. (4) xvi. pp. 142,162) he established the family Acervochalinida, making his firstgroup of the family Solida, in which Acervochalina would come.He himself suggested the name which I have adopted, and hassent me a specimen illustrating his view of the species which shouldbe assigned to the genus. The constancy in form of both this andthe following species, and their agreement in other points, show themto be no mere dwarfed forms of erect Chalinidte.Schmidt has on reconsideration (Atl. Geb. p. 38) referred Chalinalimbata to Chalinula ; but that genus is equivalent to Chalina,* This so-called variety seems, by the constancy of the peculiarities of itsexternal form, tIz. knife-like shape, two marginal rows of vents, and smoothsurface, to differ specifically from C. armigera, and may therefore stand asCladochalina pergamentacea.