128 LAWRENCE M. LAMBE ON 



0-622 mm., with an average thickness of 0'009 mm. ; forming the main skeleton. (2) 

 Small tylostyli with rounded heads (Plate III., tig. 6a), occurring at the surface ; trom 

 0-117 to 0-301 mm. long and averaging 0-008 mm. in thickness. (3) Small, minutelj^ 

 spined oxeote spicules, inflated at midlength (Plate TIL, fig. 6b) ; from 0-026 to 0-058 mm. 

 long. (4) Small, minutely spined, cylindrical spicules with rounded ends and inflated in 

 the centre ; always smaller than the oxeote spicules (No. 3), from 0-013 to 0-026 mm. long 

 (Plate III., fig. 6c). 



The main skeleton is lax and made up of the large tylost^di irregularly intermixed ; 

 the dermal skeleton is composed of the two forms of small spined spicules with loose, dis- 

 tinct brushes of the smaller tylostyli disposed at right angles to and projecting slightly 

 beyond the surface ; the small spined spicules are also distributed throughout the interior. 



Locality. — Iliuliuk Harbour and Captain's Harbour, Unalaska Island. 



SuBERiTES MONTiNiGER, Carter. 

 (Plate IV., fig. 4.) 



Suberites montiniger, Carter. 1880. Ann. and Mag. Nat. Hist., serie.s 5, vol. vi., p. 256. 



A specimen growing over portions of shells and in places thinly incrusting is doubt- 

 fully referred to this species. Its surface is raised at short intervals into low, rounded 

 monticules each with a small osculum at the top. 



The tylostyli vary in length from 0-288 to 0-471 mm. in length and have an average 

 thickness of 0-016 mm. (Plate IV., fig. 4) ; they are thickest in the centre, generally 

 slightly bent, sharply pointed at one end and terminate in a long oval head at the other. 



Locality. — Granite Cove, Port Althorp. 



SUBERITES CONCINNUS. (Sp. UOV.) 



(Plate IL, figs. 12, 12a.) 



Sponge of irregular shape, attached and growing freely ; the largest specimen in the 

 collection being 88 by 52 by 32 mm. in size. Colour, in spirit, a light yellowish to a dark 

 brown. Texture, very firm, compact. Surface, even, slightly hispid. Pores, scattered, 

 visible only in thin sections at right angles to the surface. The most perfect specimen 

 (Plate IL, fig. 12), and the only one in which oscula are seen, is small, sessile and sub- 

 spherical, measuring about 20 mm. in height and breadth ; its basal attachment is about 10 

 mm. across. Oscula small, about 0-5 mm. in diameter, each occupying the summit of a low 

 prominence. 



Skeleton. — Composed of stylote spicules arranged in a somewhat loose halichondmid 

 fashion. At the surface the styli are arranged in bundles placed side by side at right 

 angles to the surface, forming a compact cortex. It is between these surface bundles of 

 spicules that minute openings (pores) are seen, in sections at right angles to the surface, 

 leading into the interior of the sponge. The styli project but slightly beyond the surface. 



Spicules. — Megasclera ; of one kind only, viz., rather slender, straight, sharpl}' pointed, 

 smooth styli (Plate IL, fig. 12a), with evenly rounded basal ends ; varying in length from 

 0-229 to 0-301 mm., with an average thickness of 0-005 mm. There is no difference in size 

 between the spicules of the cortex and those of the main skeleton. 



Distribution. — Arctic Ocean, Behring Sea and North Pacific Ocean. 



