22 PORIFERA. II. 



arms are of equal length, in which feature this sigma quite agrees with those of as well E. decora as 

 H. claviscepta. It is also of some importance that the developmental form of this sigma has been found 

 here, as it has not been known before. 



Localitx: Ingolf, station 55, 63" 33' Lat. N., 15- 02' Long. W., depth 316 fathoms. Only one 

 specimen. 



7. E. typichela n. sp. 

 PI. I, Fig. 3. PI. IX, Fig. 2 a— c, Figs. 3—4. 



Incrusting, the surface with very small, close-set , conical projections, (end with scattered long, 

 flagelliform appendices ; the dermal membrane thin, without spicules. The skeleton consists of polysplenia/ 

 fibres, chiefly running from the base to the surface. Spongin -van ting. Spicula : Megasclera styh o-jj 



o-yj"""/ microsclera, isochelcr palmatm of two forms, larger ones 0-064 — o-ojtf"'". smaller ones 0-021 



— 0-025""". 



The specimen in hand of this species grows incrustiug on a Hornera lichenoides, but it grows 

 over more branches, so that it forms a continuous plate, and it grows quite round the Hornera so as 

 to show a surface on both sides. The greatest extent of the sponge is 30 mn \ and the thickness from 

 surface to surface reaches at most 5""". The consistency is soft. The colour (in spirit) is gray. The 

 surface is to the naked eye smooth, but under a magnifying glass it is seen to be covered with close- 

 set, conical projections owing to the ends of the fibres. Further it shows the peculiarity that long, 

 fine, flagelliform appendices formed by a spicula-fibre project scattered round on the sponge. In the 

 present state of the sponge these free fibres are lying along the surface and appear to the naked eye 

 as sinuous threads. The dermal membrane is exceedingly thin; it contains no skeleton, and rests on 

 the mentioned projecting ends of the fibres. Pores are found in the dermal membrane in the areas 

 between the projecting ends of the fibres; they are generally so close-set, that the membrane becomes 

 a network. They are round to oval, and their size was measured to 0-059 — o-i4 mm . Oscitla were 

 not found. 



The skeleton. It is a difficult task to examine the structure of the skeleton continuously on 

 account of the soft consistency of the sponge. It consists chiefly of polyspicular fibres running from 

 the base to the surface where they project and form the conical projections mentioned above. The 

 average thickness of the fibres is ca. o-03 mm . No transverse fibres are formed between these fibres, but 

 fibres or bundles of spicules are found, especially down towards the base, placed horizontally or 

 irregularly. The mentioned fibres that run from the base to the surface, are only short on account of 

 the small thickness of the sponge; but frequently they are not placed perpendicularly, but more or 

 less obliquely, and often they are very decumbent, and so become considerably longer. The projections 

 caused by the fibres, therefore, are not perpendicular to the surface, but more or less oblique. Now a 

 few of the projecting fibres are prolonged and form the mentioned long, fine appendices scattered on 

 the surface of the sponge. These appendices, which thus seem simply to be prolonged fibres, are at 

 the base a little thicker than the other projections having here a thickness of ca. o-i6 mm , but they 

 taper towards the point. They may reach a length of up to io mm . They consist of a fibre surrounded 

 by a thin layer of tissue. At the base of the fibre there are many spicules alongside, but towards the 



