ART. 12 HEXACTINELLID SPONGES — OKADA 29 



Mesamphidisks (fig. 3, e), which vary in size considerably and 

 measure 30/i to 90/x long, occur chiefly on the walls of larger ex- 

 current canals as a layer and are scattered in the parenchymalia. 

 The narrower incurrent canals are destitute of such a layer or coating 

 of mesamphidisks, being instead occupied by pentactinic pinules. 

 The shaft is slender and covered with sharp spines. In the center 

 there is a ring of longer spines. The high, bell-shaped terminal 

 disks have 10 to 12 marginal teeth, usually narrow, measuring 20/j, 

 to Wfi in lengtli and 20/a to 25/x broad. 



Micramphidisks (fig. 3. d), which are much fewer than the for- 

 mer, lie scattered irregularly in the dermal and gastral membrane; 

 still fewer are found in the choanosome. They are 15fi to 20/a long 

 and have hemispherical terminal disks with several marginal teeth. 



Although I find the outer features of this sponge peculiar, the facts 

 stated above enable me to place it systematically. At first doubting 

 w^hether it should be placed in the present genus or in some otlier 

 genus of the Hyalonematidae, or whether a new genus should be 

 established for it, I have come to the conclusion that the entire 

 spiculation, particularly the dermal pinules and the parenchymal 

 oxyhexactins with their curved rays, is in complete accordance with 

 what I find in the other representatives of Hyaloneina. 



HYALONEMA (CORYNONEMA) OWSTONI Ijima 



H ijalonenia owstoni Ijima, Zool. Anz., no. 450, p. .367, 18&4. 

 Hijaloncma clathratum Ijima, Zool. Anz., no. 459, p. 368, 1894. 



In the collection I discovered a complete specimen and two frag- 

 ments referable to the present species, obtained from Station 4958. 

 The first, specimen A, represents a complete, tolerably large, slightly 

 inflated cup. It is 46 mm high and has, at the upper free margin of 

 the cup, where broadest, a transverse diameter of 55 mm. The outer 

 dermal surface is composed of a fine and nearly uniform smooth and 

 even network. The inner surface is perforated by numerous more 

 or less circular ajDertures, 1 mm to 6 mm wide, which are the open- 

 ings of the excurrent canals into the cup cavity, which is the gastral 

 cavity of the sponge. These canal mouths are irregularly distributed 

 and decrease in size toward the upper, free margin of the funnel 

 wall. There is no trace of an oscular sieve plate. 



Table 11. — Record of specimens of Hyaloneina (Corynonema) owstoni 



