NO. 2247. SPONGES FROM NORTHWESTERN PACIFIC— HOZAWA. 543 



surfaces are smooth. The color in alcohol is white with a somewhat 

 grayish tint. The texture is very compact and rather hard, 

 lation of small tangential triradiates, to which there may be added 

 a small number of specially large tangential triradiates and some 

 microxea in scattered distribution. The skeleton of oscular margin 

 is a close interlacement of small triradiates and quadriradiates, both 

 which have strongly divergent paired rays and downwardly directed 

 basal ray. There may be found in addition some triradiates of an 

 unusually large size. 



Structure. — The canal system is leuconoid. The wide inhalant 

 canals, starting from beneath the dermal surface, run centripetally 

 into the chamber layer, becoming narrower as they divide into 

 branches. The exhalant canals are also wide and branching. The 

 gastral apertures, by which the exhalant canals open into the gastral 

 cavity, are circular or oval measuring up to -| mm. across. The 

 flagellate chambers, closely packed in the chamber layer, are oval or 

 nearly spherical with diameter of 30-60 [x. 



The dermal skeleton is made up of large and small triradiates 

 placed tangentially in several confused layers. On the dermal sur- 

 face are found microxea in thinly scattered distribution. The skele- 

 ton of the chamber layer likewise consists of large and small trira- 

 diates in dense and irregular disposition. Along the larger exhalant 

 canals there occur a different sort of triradiates in addition to some 

 quadriradiates with apical rays projecting into the canal. The gas- 

 tral skeleton is fairly well developed ; it is composed of a dense reticu- 



Spicules. — The larger dermal triradiates {a) regular or subregular. 

 Rays nearly straight, gradually tapering toward the pointed end, 

 very variable in dimensions, 200-800/i long and 20-90/i thick at base. 

 The smaller dermal triradiates (&) slightly sagital; the rays nearly 

 uniformly thick, not lying all in one plane. Basal ray slightly longer 

 than paired rays, straight, usually 200-300^ long and 16-28/x thick 

 at base. Paired rays slightly curved, 150-270/li long. 



Triradiates of chamber layer (c) regular, very variable in size. 

 Rays straight, 350-800/x long and 40-90/x thick at base. 



Quadriradiates of the larger exhalant canals {cl) have gradually 

 tapering and sharply pointed rays of nearly equal thickness, the 

 facial rays not lying in one plane. Basal ray straight, about 200|u, 

 long and 16ii. thick at base. Paired rays more or less curved around 

 the exhalant canals, about 200;u, long and l^ix thick at base. Apical 

 ray much shorter and thinner than facial rays, slightly curved and 

 very finely pointed, about 50fi long and 8/x thick at base. 



Triradiates of the larger exhalant canals {e) nearly similar to the 

 above quadriradiates, only differing in the absence of apical ray. 



Gastral triradiates (/) strongly sagittal. Basal ray straight, 

 sharply pointed, thinner and shorter than paired rays, 80-150/^ 



