122 LAWRENCE M. LAMBE ON 



frequently develop a few spines toward the pointed end ; varying in length from 0'209 to 

 0-235 mm., with an average width of 0-013 mm. The basal end when not spined generally 

 terminates centrally in a single point. (2) Tylota (Plate III., fig. 3c) more slender than 

 the styli, straight or slightly curved with a pronounced inflation at either end which becomes 

 attenuated and pointed at the outer termination ; size 0-196 by 0-009 mm. This form of 

 spicule also occurs in considerable numbers throughout the main skeleton. (h) Microsclera ; 

 (1) isochelœ (Plate III., fig. 3d) from 0-022 to 0-052 mm. long. (2) Sigmata (Plate III., 

 figs. 3e, 3f ), simple and contort ; from 0-019 to 0-39 mm. long. Both forms of microsclera 

 are abundant in all parts of the sponge especially in the dermal membrane. 



There are a number of specimens, the largest of which is about 120 mm. across. 



Distribution. — Behring Sea and î^orth Pacific Ocean. 



Myxilla Amaknakensis. (Sp. nov.) 

 (Plate IL, figs. 10, 10a— e.) 



Sponge (Plate II., fig. 10) thickly incrusting or growing in irregular masses. The 

 largest specimen in the collection is nearly 60 mm. across and 35 mm. high. CdIoio; in 

 spirit, a rather dark j-ellowish-brown or, when dry, very much lighter. Tej:ture, moderately 

 firm. Surface, undulating, rough, with short, broken up ridges or separate elevations 

 between which wind depressed areas or furrows. Dermal membrajie, thin, delicate, spicu- 

 lous. Oscula well marked, distinct, usually elevated, about 2-5 mm. in diameter. Pores 

 scattered, averaging 0-098 mm. diameter. 



Skeleton. — (a) 3fain ; a definite network of stylote spicules inclosing triangular or 

 quadrangular meshes having sides of one spicule's length and made up of from one to four 

 or five spicules placed loosely together. This arrangement of the main skeleton is very 

 typical of sponges belonging to this genus. [h) Dermal. The ridges and elevations of the 

 surface are composed of an aggregation of tornota and the dermal membrane is abundantly 

 supplied with the same spicules strewn about horizon tall \- in it without order. 



Spicules. — (a) Megasclera of two kinds : (1.) Small, stout, entirel}' spined styli (Plate 

 IL, fig. 10a) with sharp points ; average size 0-144 by 0-013 mm., forming the main 

 skeleton. (2) Sparsely spined tornota (Plate IL, figs. 10b, 10c) with rather blunt ends ; 

 found throughout the main skeleton, but chiefly occurring in the dermal skeleton ; average 

 size 0-137 by 0-008 mm. (6) Microsclera; small isochelœ, with strongly curved shafts, 

 (Plate IL, figs. lOd, lOe) very aljuiidant in all parts of the sponge ; average length 0-022 

 mm. 



Distribution. — Behring Sea and Xorth Pacific Ocean as far south as Vancouver Island. 



'& 



Myxilla firm a. (Sp. nov.) 



(Plate III., figs. 4, 4a— f) 



Sponge (Plate III., fig. 4) massive, of irregular shape, represented in the collection by 

 a large specimen, roughly, 111 mm. long, 90 mm. broad and 55 mm. high, preserved in 

 alcohol. Colour, in spirit, brownish-yellow. Texture, firm, compact with no elasticity. 

 Surface, uneven, rough with narrow ridges beset with small sharp protuberances, forming a 

 network over most of the surface of the sponge but more particularly over the depressed 

 areas. Dermal membrane comparatively thick and tough, spiculous, stretched across the 



