70 



PEOCEEDIlsrGS OF THE NATIONAL MUSEUM 



VOL. 81 



Specimen B is barrellike in shape and measures only 30 mm in 

 height, with a roundish osculum 10 mm in diameter. It was directly 

 and firmly attached to stones with the basal surface. The wall is 

 2 mm thick at the base and gradually becomes thinner toward the 

 oscular margin, which is 0.8 mm thick. 



Spictilation. — The following description applies to the first and 

 larger specimen (A), unless otherwise indicated: 



The parenchymalia are all slender diactins of variable thickness, 

 measuring lO^u to 30/a broad and 1 mm to 2 mm long. Both ends of 



Figure 7. — Hyalascus attcnuatus, new species: a, Gastral hexactin, X 175+ ; 

 Z), dermal stauractin, X 175+ ; c, hemihexactinic oxyhexaster, X 375; d, 

 hemihexactinic oxyhexaster, X 375 ; e, hexactiaic oxyhexaster, X 375 ; 1, 

 oxyhexaster, X 375 



the diactins usually are conically pointed and beset with micro- 

 tubercles on the surface. Sometimes each is spherically expanded, 

 showing a moderately large knoblike swelling. The diactins occur 

 either individually or are combined into long bundles. Besides this 

 spicule, shorter and slenderer diactins, which are almost entirely 

 smooth on the surface, frequently occur in the parenchyme. Very 

 strong and large diactins are only occasionally found among the 

 foregoing. They are more commonly present in the lower regions of 



