PORIFERA. II. 



191 



preceding species, varying only between fourteen and fifteen, and the number was almost always four- 

 teen, only once fifteen teeth were counted. The length of birotulse is o - oi8 — o-02i mm , the thickness of 

 the shaft is ca. o - ooi4 mm , and the breadth across the circle of teeth is ca. o - oo6 mm . The microscleres 

 are found throughout the sponge, the ancorse are especially numerous in the dermal membrane. Biro- 

 tula;, as usual, are by far the most numerous. 



locality: Between Iceland and the Faroe Islands, 64 56' Lat. N., n° 48' Long. W., depth 115 

 fathoms (Ad. Jensen, the cruise of the Michael Sarss 1902). One specimen. 



6. I. rotulancora 11. sp. 

 P1.XVIII, Fig. 6 a— g. 



Form'/ The .surface smooth or slightly shaggy. The dermal membrane a thin film, supported by 

 highly recumbent, often quite horizontal, bundles of dermal spicules. The skeleton consisting of spicules 

 and a few spicula-bundles, placed irregularly. Spicula: Megasclera: the skeletal spicules styli 0-40 — 

 °'55"""> th e dermal spicules tylota o-jo — 0-41"""; microsclcra of two forms, isancorce unguifera with hvelvc 

 to seventeen teeth, of which either all are free, or one or two are zmited with the shaft, 0-030 — 0-040™", 

 birotulce with nine to twelve teeth 0-018 — 0-032""". 



We have only one specimen, which is, moreover, a fragment, or, at all events, torn off from 

 the underlayer; the sponge, I suppose, has formed a cushion-shaped incrustation, but its form cannot 

 be decided with certainty, and the question might perhaps be of a fragment of a more or less leaf- 

 shaped sponge. The specimen has a greatest extent of 22'"'", and the thickness is ca. 4"™. The colour 

 (in spirit) is light brown. The consistency is middle firm. The surface is smooth or at most slightly 

 shaggy. The dermal membrane is a thin film, contracting when detached; it is supported by bundles 

 of dermal spicules. Pores and oscula were not seen. 



The skeleton. The slight material in hand has rendered it impossible to examine the skeletal 

 structure as thoroughly as was to be wished. The dermal skeleton consists of bundles of dermal 

 spicules, highly recumbent, often quite horizontal. The main skeleton seems to consist of spicules and, 

 here and there, of spicula-bundles, placed irregularly, and forming neither meshes nor fibres, at most 

 here and there arranged a little loosely in a band-like way. A distinct, but little copious amount of 

 spongin is found where the spicules are united. 



Spicula: a. Megasclera. 1. The skeletal spicules are styli; they have a curve near the 

 head-end, and are evenly and long tapering, the outermost point itself is often somewhat stubby. 

 Their length is 0-40 — o-55 mra , the thickness is ca. croio — o-oi28 mm . The longest ones are not the thickest 

 ones. 2. The dermal spicules are tylota; they are straight, only rarely a little curved, and of about 

 equal thickness throughout the length; they are somewhat varying in length, from 030 — o'4i mni , most 

 frequently the length is midway between the given measures; the thickness is 0-004— croc^"" 1 '. The 

 tylota taper a little towards one end, and this end, therefore, has a more distinctly marked swelling. 

 b. Microsclera ; these are isancorse unguiferse and birotulse. 1. The ancorse of this species are inter- 

 esting by forming a distinct transition to birotulse. They have many teeth, twelve to seventeen, when 

 they are counted all round. When the ancora is seen from the end, the circle of teeth is quite, or 



