SPONGES FEOM THE WESTEEN COAST OF NORTH AMERICA. 129 



Polymastia lasanoides. (Sp. nov.) 

 (Plate IV., figs. 5, 5a— c.) 



Sponge (Plate IV., fig. 5) sessile, thin, coatiiig a considerable area, represented by a 

 single specimen measuring 115 mm. across, 8 mm. thick in the centre and thinning ofi" 

 toward the edges. Colour, in spirit, a light yellow. Texture compact, leathery. Surface 

 even, hispid, bearing in places low, warty protuberances averaging 5 mm. in breadth. 

 Oscilla. Translucent rings are disposed at intervals over the surface and also occupy the 

 summit of the mammiform protuberances ; each ring incloses what appears to be a minute 

 osculum averaging 0'68 mm. in diameter. Pores (f) scattered. 



Skeleton. — Stout fibres of long styli pass toward the surfixce, entering but not reaching 

 the surface of a cortical layer of irregularly disposed smaller styli. The projection of some 

 of the smaller styli beyond the surface causes a slight hispidity. The translucent rings on 

 the surface are seen to be caused by the absence of the cortical layer of spicules ; the stout 

 fibres here continue be^'ond the surface, causing a circular or star-shaped area surrounding 

 each osculum to be strongly hispid. îfear the edge of the sponge in places, and where 

 portions of the surface are below the general level, a marked hispidity is also apparent. 



Spicules. — 3Iegasciera ; styli, of three sizes. (1) Large, gradually and sharply pointed, 

 smooth tylostyli (Plate IV., fig. 5a), thickest at midlength and generally with a well devel- 

 oped head ; up to 1"50 by 0'020 mm. in size ; forming the fibres and projecting beyond the 

 surface in places, viz., surrounding the oscula, near the edge of the sponge and where the 

 surface is sunken. (2) Short, sharply pointed, smooth tylostyli, thickest at the middle, 

 with a strongly marked head (Plate IV., fig. 5b) ; average size 0-479 by 0-013 mm. ; com- 

 posing the dermal layer. A noticeable feature in this sponge is the absence of a regular 

 radiating arrangement of the spicules of the cortex ; the spicules are closely intermixed and 

 lie at all angles to the surface, those that project beyond it causing a slight hispidity. (3) 

 Very small, slender tylostyli with rounded heads (Plate IV., fig. 5e) ; average size 0-117 by 

 0-008 mm. ; distributed in large numbers throughout all portions of the sponge, especially 

 in the soft parts between the fibres. 



Locality. — Behring Island. 



Desmacella pennata. (Sp. nov.) 

 (Plate IV., figs. 6, 6a— d.) 



Sponge (Plate IV., fig. 6) thinly coating, forming small irregularly shaped patches; the 

 largest of the four specimens representing the species is about 50 mm. acr(3ss and does not 

 exceed 5 mm. in thickness. Colour, in spirit, dark grayish-brown. Texture firm with little 

 elasticity. Surface hispid, rather uneven, traversed in all directions by shallow ramifying 

 grooves which in many places diverge from a common centre forming irregularly star-shaped 

 depressions. The surface between the grooves is at times considerably elevated. Dermal 

 membrane spiculous, adhering firmlj' to the spicules that project beyond it. Oscula small, 

 dispersed, circular, about 0-131 mm. in diameter. Pores scattered, averaging 0-032 mm. in 

 diameter. Found growing on rocks at low tide. 



Skeleton. — Fibres, composed of stout styli with a large proportion of horny matter, 

 ascend from the base to the surface remaining separate until near the surface where they 



Sec VI., 1894. 17. 



