94 PROCEEDINGS OF THE NATIONAL MUSEUM vol.81 



ures 80/x to llOfx, while in the latter it is 150/i to 210ju, across. Of 

 the hemihexactinic forms, the total number of terminals to the 

 entire rosette may vary from 5 to 11, indicative in each case of the 

 number of the principals that remain biterminal and of those that 

 become uniterminal. 



Much less numerous than the oxyhexasters are the microdiscohex- 

 asters, which vary considerably in size, measuring 2>0fx to 60ju, in 

 diameter. They are thinly distributed both subdermally and sub- 

 gastrally, though they seem to be much commoner in the gastral re- 

 gions. The shape is spherical ; the terminal disk is minute, not pin- 

 headlike, but is a small laterally expanded disk. 



Genus ACANTHASCUS F. E. Schulze, 1886 



ACANTHASCUS PACHYDERMA, new specieB 



Figure 12 ; Plate 5, Figure 1 



This species is based on a single complete specimen (holotype, 

 U.S.N.M. No. 22123) collected from a depth of 229 fathoms south- 

 east of Shimushir Island, Kuriles (Station 4803). It has an elon- 

 gated barrel shape. The lower end is somewhat contracted into 

 a stalklike base, 27 mm broad, gradually becoming broader toward 

 the upper end. The total height is 88 mm; the greatest breadth 

 near the anterior end of the body is 39 mm. The osculum at 

 the superior end of the stock is elliptical in form, the greater diameter 

 being 18 mm and the smaller 11 mm. The deep gastral cavity ex- 

 tends almost into the stalklike base. The body wall in the middle 

 is as thick as 10 mm and is of nearly the same thickness toward the 

 simple-edged oscular margin. 



The external surface is quite smooth, but shows indications of a 

 number of small and large tubercles, measuring 1 mm to 3 mm across 

 in the lateral side of the entire stock. The more prominent of these 

 tubercles may have been 2 mm in height. The wall is firm, on ac- 

 count of the closelj^ interwoven state of the hypodermal spicules as 

 well as of the small size of the canals. Nearly all the irregularly 

 quadrate-meshed dermal latticework is torn off. It partly covers the 

 incurrent apertures, which are less than 2 mm in diameter. Their 

 apertures are irregularly placed and are indistinctly visible through 

 the latticework. The gastral surface appears smooth, but the excur- 

 rent apertures may be distinctly observed, 2 mm to 3 mm in diam- 

 eter, distributed irregularly. 



Spiculation. — Principal parenchymalia are fairly long diactins, 

 4.5 mm or more in length and up to 20/x in thickness at the middle. 

 They taper gradually toward the conically pointed or rounded ends, 

 the surface of which is much less strongly roughened than that of 



