158 PORIFERA. II. 



Locality: 62°n'Lat.N., 19 36' Long. W., depth 1142 fathoms. (The cruise of the fishery investi- 

 gation steamer «Thor», 1903). 



Geogr. distr. Fristedt has the species from East Greenland, 65 30' Lat. N., depth 130 fathoms. 



3. L. fragilis Frstdt. 

 PL V, Figs. 7—8. PL XVI, Fig. 1 a-g. 



1885. Hastatus fragilis Fristedt, Kgl. Sv. Vet. Akad. Handl. Bd. 21, Nr. 6, 35, Taf. Ill, Fig. 6 a— h. 



Tli c form somewhat varying, forming thick incrustations, or the sponge irregularly massive or 

 erect, formed like an irregular, thick leaf. The surface grooved and finely shaggy. The dermal mem- 

 brane a very thin film, in some places with erect bundles of dermal spicules, in other places with spicules 

 horizontally in the membrane. Oscula scattered, or found only on one side. The skeleton an irregular, 

 polyspicular reticulation of triangular, quadrangular, or polygonal meshes; in the leaf-shaped specimens 

 longer fibres may be found. Spicula : Megasclera : the skeletal spicules very finely spiued or smooth styli 

 0-29 — 0-40""", the dermal spicules tornota 0-20 — 0-268"""; microsclera of two forms, chelce arcuatcr o-ojy 

 — crodo""", sigmata o'oiS — o'02j""". 



Of this species we have a rather large material, but it consists mostly of fragments or much 

 damaged specimens. To judge from this material the species may vary somewhat with regard to its 

 outer form. Sometimes it forms only an irregular, thick incrustation, but the larger specimens seem 

 always to rise from the underlayer, growing upwards and assuming a more or less irregular leaf-shape. 

 These leaf-shaped specimens are always rather thick. The specimens are attached to plate-shaped 

 Bryozoa or have their bases expanded over bottom material of different sorts. The largest specimen 

 which seems to be the lower part of a leaf-shaped individual, has a greatest extent of ca. 45 mm , and a 

 thickness of ca. io mm ; a rather regularly leaf-shaped fragment is of similar dimensions. Entire speci- 

 mens of the sponge are evidently much larger. The massive specimens are smaller. The colour (in 

 spirit) is a lighter or darker grayish yellow. The consistency is rather firm, but brittle and fragile, 

 and this is surely the reason, why the specimens are in a so highly damaged condition. The surface 

 is grooved, about as in M. iucrustaus, and it is finely shaggy from projecting spicules. The dermal 

 membrane is a very thin and transparent film ; it rests on the skeleton below, and is partly supported bv 

 this skeleton, partly by special dermal spicules. Pores are found in the membrane, often closely gathered, 

 so that pore-sieves are formed. Their size was measured to 0-047 — o-2o, mm . In the markedly leaf-shaped 

 specimens the pores seem only to occur on one side, while oscula belong to the other side; in the 

 irregular specimens, on the other hand, there is no definite localisation of oscula and pores. Oscula 

 are seen as circular openings scattered on the side that has no pores; they are of an average size of 

 1 — 2 ram . The sponge is set through very closely with canals running from one side to the other, not, 

 however, running straight across, but sinuous and branched in different ways. Some of the largest of 

 these canals open on the oscular side as oscula, and in the oscular canal a great many smaller canals 

 are seen to open. When the dermal membrane is removed from the opposite side, a great many close- 

 standing incurrent canals are here seen. 



The skeleton. The dermal skeleton may be somewhat different in different places of the sponge; 



