PORIFERA. III. 67 



but the dermal spicules are polytylote strongyla and the chelae are very strongly curved; it is also 

 related to H. similis, but it is, as mentioned under this species, distinguished by the small styli being 

 straight, and by differences in the dermal spicules and the chelae; also the styli intimitis are distinctly 

 divided into two groups. 



Locality: Station 7, 63 13' Lat. N., 15 41' Long. W., depth 600 fathoms, and at 6i° 09' Lat. N., 

 7 54' Long. W., depth 180 fathoms, (Ad. Jensen, the crnise of "M. Sars" 1902). Two specimens in all. 

 The localities lie South of Iceland and West of the Faroe Islands. 



21. H. occulta Bow. 

 PI. Ill, Fig. 6, PI. VII, Fig. 8. 



1874. Hymedesmia occulta Bowerbauk, Mon. Brit. Spong. II, 250, III, PI. LXXIX, figs. 9 — n. 

 1894. Desmacidoii occultuui, Hanitsch, Trans. Liverp. Biol. Soc. VIII, 180. 

 1894. Hymeraphia occulta, Topsent, Rev. Biol, du Nord de la Fr. VII, 12 et 21. 



1904. Leptosia occulta, Topsent, Resultats des camp, scient. du Prince de Monaco, Fasc. XXV, 186, 

 PL XV, fig. 1. 

 Incrusting : surface smooth, generally with a number of papilla, bearing oseula and pores, and 

 with a dense skeleton of dermal spicules in the wall. Spicula: megasclera; the skeletal spicules acantho- 

 styli with a small, but distinct head, divided into two groups, larger, only spirted below, 0-4*7 — rrg""", 

 smaller, entirely spined, 0-119 — 0-26"""; the dermal spicules foruota to oxea o-jj — o-$o mm ; mierosclera 

 chelce arcuatce with relatively small end parts, 0-034 — 0-040""". 



Of this species we have some specimens growing on stones, pebbles, small shells and one on 

 a tube of Placostegus tridentatus. Most specimens are rather small, only reaching to an extent of 

 I2 n,m ; only two specimens, growing on larger stones, have a greatest extent of 18 and of 20 mm ; the 

 thickness reaches at most i mm . The colour (in spirit) is whitish grey or brownish. The surface is 

 nearly smooth, but seen with a lens it shows small, ptiuctiform projections, caused by the skeletal 

 spicules reaching the dermal membrane, but not piercing it. The surface may otherwise have a 

 different aspect; in some specimens, especially the small ones, it shows no or only few and imper- 

 ceptible papillae, but in the larger and best developed specimens the surface bears a number of 

 papillae, often rather close-standing; the papilla; are conical or nearly cylindrical, and may reach to a 

 height of about 1*5 mm , but the exact length cannot be given, as one side of the wall is generally 

 shorter than the other, the papillae lying somewhat down towards the surface. The dermal membrane 

 is a transparent, somewhat solid and easily separable membrane; it has an irregular skeleton of hori- 

 zontal spicules and is more or less densely filled with chelae, which form, however, no layer. Oseula 

 and pores: the papillae mentioned are both oscular and pore-papilla;. The oscular papillae are more 

 conical and tapering than the others and have a simple oscular opening at the summit; the pore- 

 papilhe are broader at the tip and have here a membrane with pores. Bowerbank, who had 

 only one small specimen, does not mention papillae; Topsent, on the other hand, has perhaps 

 seen something of the kind, as he says (1. c. 186) that the sponge somewhat resembles a small 

 liamacantha. 



