120 LAWRENCE M. LAMBE ON 



Skeleton.— ^(a) Maiv ; composed of stout stylote spicules, arranged in rather loose 

 plumose fibres running to the surface, which are crossed at irregular intervals by loose 

 secondary fibres or individual spicules, (h) Dermal; brushes of small styli, with outwardly 

 directed points, supporting the dermal membrane, beyond which thej' project Imt slightly, 

 are interlaced with similar styli lying horizontally. The brushes are the surface termi- 

 nations of the fibres of the main skeleton, and they, together with the horizontally disposed 

 styli, form a thick dermal skeletal zone at the surface. A large proportion of rather trans- 

 parent spongin is present. 



Spicules. — (a) Megasdera ; of two sizes. (1) Stout, somewhat curved, smooth styli 

 with the basal end very slightly enlarged and tapering gradually to an acute iioint at the 

 other end (Plate II., fig. 8a) ; up to 1-10 by 0-041 mm. in size ; forming the main skeleton. 

 (2) Small, slender, not very sharply pointed, smooth styli (Plate II., tig. 8b) ; confined to 

 the dermal skeleton ; varying in size from 0-176 by 0-009 to 0-478 by 0-013 mm. (h) Mivro- 

 sclera ; of two kinds ; (1) very small isochelse (Plate II., fig. 8c), with curved shafts and 

 three minute teeth at each end ; 0-019 mm. long. (2) Simple sigmata (Plate IL, tig. 8d) ; 

 0-013 mm. in length. The chelae of this species differ only from the characteristic cheliB 

 of the various species of Cladorhiza in being equal ended instead of unequal ended. 



Locality. — Aleutian Islands. 



lOTROCHOTA MAGNA. (Sp. nOV.) 



(Plate III., figs. 2, 2a— d.) 



Sponge (Plate III., fig. 2) massive, of irregular shajae, represented in the collection by 

 two specimens, one preserved in alcohol, about 105 mm. long, 50 mm. broad and 50 mm. 

 high, the other dry, roughly 150 mm. by 115 mm. and 70 mm. high. Colour, in spirit, a 

 yellowish-brown. Texture firm but spongy. Surface intersected by broad, raised, smooth, 

 flat ridges, with abrupt sides, which branch in different directions and enclose sunken areas 

 having a verj' uneven surface. Dermal membrane, tough, spiculous, separated with diffi- 

 culty from the underlying tissues. Oscula, circular openings about B-5 mm. in diameter, 

 occupj'ing the raised ridges and at short intervals apart, often in a uniserial row. They are 

 the outer terminations of broad canals leading from the inner parts of the sponge. Pores, 

 scattered, about 0-041 mm. in diameter. 



Skeleton. — Consisting of an irregular reticulation of rather loose fibres of stout styli 

 with a moderate proportion of horny matter. At the surface is a thick layer of smaller 

 styli, interlaced horizontally, supporting the dermal membrane. 



Spicules. — (a) Megasdera ; of two sizes. (1) Stout, often slightly bent, rather abruptly 

 but sharply pointed smooth styli with broadly rounded basal ends (Plate III., fig. 2a) ; aver- 

 age size 0-438 by 0-024 mm. ; forming the main skeleton. (2) Slender, smooth, generally 

 somewhat bent, sharply pointed styli (Plate III., fig. 2b) ; varying in length from 0-242 to 

 0-333 mm. and in thickness from 0-006 to 0-009 mm. ; composing the dermal skeleton and 

 distributed in considerable numbers throughout the main skeleton. [h) Microsclera, 

 amphiasters (birotulates) with straight shafts and with from fourteen to eighteen minute 

 teeth encircling the inner edges of the hemispherical terminations; length 0-229 mm.; 

 very abundant in all parts of the sponge. On account of the small size of the spicule and 



