ART. 12 HEXACTINELLID SPONGES OKADA 85 



The pentactins are much like those in the dermal layer, but tlie 

 prickles over their surface are not so prominently developed. They 

 rarely occur in this layer. The prominent sixth ray knob is usually 

 found in these spicules, though absent in the dermal pentactins. 



The oxyhexaster consists of normally developed oxyhexaster, hemi- 

 hexactinic (fig. 10, r/, e), and hexactinic (fig. 10, c) forms. The 

 former oxyhexasters are not so numerous. They occasionally occur 

 in the ectosome and in the endosome, and far more rarely in the 

 parenchyme. They measure 108/x in diameter. From each ex- 

 ceedingly short principal, there diverge usually two, thin, often 

 slightly strong, obsoletely rough-surfaced, and nearly straight ter- 

 minals. Frequently the last two forms ave found throughout the 

 sponge, being especially abundant in the choanosome. No special 

 mention is made of the hemihexactinic and hexactinic forms. Gen- 

 erally speaking, the central nodes of these spicules are distinct, and 

 the surface of all the rays is rough. 



The macrodiscohexaster (fig. 10, /) is somewhat smaller than that 

 of A. TTiUsukurli, is nearly spherical in shape, and measures 90/x in 

 diameter. It is not so well supplied with terminals; these are very 

 thin and generally not straight. No more than five terminals arise, 

 not in a circle but promiscuously from the disklike expansion of 

 each very short broad principal. The terminal disks are very small 

 and are furnished with three or four sharply pointed claws. This 

 macrodiscohexaster is found chiefly in the dermal and gastral layers, 

 and frequently quite abundantly in the choanosome. 



The microdiscohexaster (fig. 10, r/) is small, only 28ju, in diameter, 

 and spherical in shape. I have found it fairly numerous in the 

 gastral and dermal membranes, but in the parenchyme it is exceed- 

 ingly rare. 



AULOSACCUS SOLASTER, new species 



FieuRH 11 



This species is represented in the collection by a large fragment 

 (holotype, U.S.N.M. No. 22109) that seems to be the superior part of 

 an entire stock. It was obtained southeast of Shimushir Island, 

 Kuriles, at a depth of 229 fathoms (Station 4804). The osculum 

 may attain 140 mm in size. The body wall is very thick, measuring 

 30 mm at the inferior region, and becomes thinner toward the oscular 

 margin. It has a yellowish-white color in alcohol. 



Spiculation. — The parenchymalia are all slender diactins of varia- 

 ble thickness. Their ends are usually beset with microtubercles and 

 are mostly conically rounded. The diactins occur either singly or 

 combined into long threadlike bundles. In the latter case, they are 

 curled strongly among the parenchymalia, commonly about 1.5 mm 

 thick. These diactins are long, attaining a length of 4.25 mm to 



