AiiT. 12 HEXACTINELLID SPONGES — OKADA 59 



to 60/A long. Tlie tangential rays are simple, straight, prominently 

 tuberculous at the weakly blunt or conically pointed ends, and twice 

 or four times as long as the distal mj, measuring 130ju, to 200/^ in 

 length. The proximal unpaired ray is nearly similar in shape and 

 generall}^ much longer than the paratangentials. 



The gastralia are stout, straight diactins with a more or less 

 clearly defined swelling at the center, measuring SO^a in breadth. 

 Their ends are conically pointed and are always covered more or less 

 densely with small pointed tubercles. The spicule is usually very 

 sparsely covered with such protuberances throughout its entire 

 length. The length of these sj^icules varies considerably, from about 

 1.2 mm to 1.5 mm or more. Besides this diactin in the gastral layer, 

 there are frequently pinularlike hexactins, which are nearly similar 

 to those of the dermalia. The presence of the latter spicule, the 

 hexactin, is quite distinctive of the members of Aphrocallistes ; but 

 aleutiaim is seemingly more similar to Hexactinella than to Aphro- 

 callistes in dermal and gastral sf)iculations. 



The scopulae are numerous, are arranged horizontally to the sur- 

 face, and are of two kinds. One is small, measuring 250/a to 300/a in 

 length, and the other is larger, 400/^ to 500/x long. In the larger type, 

 the dermal branches usually number 4 or 5 and are uniformlj^ 

 bent outward in a club-shaped manner. The branches, which arise 

 from a comparatively short thickening at the distal end of the shaft, 

 measure 130/t to 150ju, in length. They are nearly cylindrical, either 

 of nearly uniform thickness throughout or basally slightly thin and 

 terminally thickened in a knot-shaped manner at the distal end and 

 uniformlj^ and densely covered on the entire length witli minute 

 spines, directed obliquely backward. The shaft usually measures 

 400/x in length, becoming gradually tapered toward the conically 

 pointed end. In a small one, the terminal branches usually number 

 four, running nearly parallel toward the thickened club-shaped ends. 

 They are covered with small, slender, oblique spines, which are di- 

 rected backward, the spines on the distal knot-shaped thickening 

 being slightly stouter. The shaft is generally simple, straight, 200/i, 

 to 250/* long, and gradually tapered toward the pointed end. It is 

 rough at the end, but for the remainder of its length is entirely 

 smooth. The chief characters aside from the one just described in- 

 clude the following : The distal thickening of the shaft is indistinct 

 and the branches arising from the margin extend upward, being 

 nearl}^ parallel to each other, and uniformly thickened throughout 

 toward the small club-shaped thickening. 



Uncinates, varying in length and thickness, are found close to the 

 dictyonal honeycomb. They are arranged horizontally or obliquely 

 to the surface and usually penetrate the whole thickness of the body 

 wall. The outer half of the spicule, nearer to the dermal surface, is 



