44 



PORIFERA. I. 



the Specimens have a somewhat darker colour. The largest specimen has a greatest extent of ca. ao'""". 

 The spicules are somewhat varying in length, the average length being ca. 0-14"""; they are also rather 

 varying in thickness, the average thickness may be given as o'Oo6'""', but it may be somewhat greater, 

 and it may go down to 0-003'"'". 



Locality: All the specimens are from JuHanehaab (inspector Ryberg). From the Swedish Riks- 

 museum we have received a specimen growing on a Balanoid, taken on the expedition of Ingegerd> 

 and «Gladan» 1871 in the Davis Strait 63° 47' Lat. N., 52 ^ 26' Long. W., depth 35 fathoms. 



Geagr. distr. This species seems to be almost cosmopolitan having been found between 80' 

 and 10° Lat. N. ; it is, however, not to be forgotten that the determinations cannot alwa^'s be regarded 

 as reliable. Besides in the Davis Strait it has been taken at Spitzbergen, depth about 12 fathoms 

 (Fristedt 1. c); it occurs further at the coast of Bohuslan (Fristedt 1. c); it is common on the English 

 coasts and on the French side of the English Channel; by the Challenger Expedition it is mentioned 

 from the Philippine Islands, on a depth of 95 fathoms; finalh- it is mentioned from British Colombia 

 (Lambe: Sponges from the Pacific Coast of Canada. Transact. Roy. Soc. Canada XI, 1893, sect. IV, 26); 

 this determination, however, is doubtful, as the length of the spicules is given to be o-iii — 0-098'"'". 



8. R. tubulosa Frstdt. 

 PI. II, Fig, 5, PI. XI, Fig. II a, b, c, Fig. 12. 

 1887. Rnierra tuhilosa Fristedt, Vega Exp. vetensk. lakttag. IV, 419, PI. 24, fig. i. 



The sponge is typically foniicd as rather fhic/c incrustations, crusts, or ciisJiions, provided with 

 more or fewer, higher or lower, conical oscular tubes; but the form may be quite irregular. The dermal 

 membrane is thin, without spicules, the ends of the fibres project., and therefore the surface is finely 

 shaggy. Oscula arc found o?i the summit of the oscular cones. The skeleton consists of a somewhat 

 irregular network of polyspicular fibres running towards the surface, and transverse spicules standing 

 singly. Spictila are slender, someruhat curved oxea with a tapering of varying length, and they may be 

 rounded; the length is o-iy — 0-208""". 



The specimens in hand of this species form more or less irregular incrustations on Alcyonidium 

 gelatinosum., shells, Balanoids, and Sabella-tubes; they are provided, at all events the larger specimens, 

 with one or several, rather regular, conical tubes, which, however, are often very low. The largest speci- 

 mens have a greatest extent of ca. 60'"'", and the greatest height of the tubes is ca. 18'"™. In one of the 

 specimens on the other hand, which is of a similar size, the tubes have only a height of ca. 6""'". When 

 several tubes are found, there may be great difference with regard to their distance from each other, 

 and they are more or less steep in proportion to this distance being greater or smaller; thus in 

 a specimen with a greatest extent of 33'"'", we find seven tubes, and the distance between them is 

 5 — 9'"'", from one osculum to the other, but generally the distance is greater. The consistency some- 

 times is rather soft, sometimes more firm. The colour (in spirit) is light grayish-yellow, and the sur- 

 face has the netlike appearance, characteristic in so many i?^«/(-^-a-species, on account of the many 

 small, close-set, round subdermal cavities. The surface is finely shaggy from the projecting spicules. 

 The dermal membrane is thin, without spicules; no special dermal skeleton is found, but the membrane 

 is supported by the skeleton below, and pierced by the ends of the fibres. The pores are small, most 



