ART. 12 



"HEXACTINELLID SPONGES — OK ADA 



66' 



measures 3 mm; and the thickness of the rays reaches COju, near the 

 central node. 



As described by Ijima, the discohexaster shows considerable vari- 

 ations in both size and appearance in the same specimen. This con- 

 dition is also found in the present specimen. In it I have discovered 

 three forms of discohexasters, which are seen in the Tokyo University 

 Faculty of Science specimen No. 436 of this species, which was taken 

 outside of Okinose in the Sagami Sea. The largest one, which 

 measures 80/x, in diameter, has three terminals, similarly thickened 

 throughout; the intermediate one, which measures 60;li in diameter, is 

 provided with four to five terminals; while the smallest one, 4:5ju, in 

 diameter, has more numerous delicate terminals, nearly resembling 

 the so-called microdiscohexasters of certain other rossellids in ap- 

 pearance. In general, the number of terminals varies with different 

 sizes of rosette, the smaller the rosette the fewer the terminals are 

 in number. 



Identical oxyhexactins, as well as canalaria and parenchymalia, 

 occur in great abundance. 



The strongiloplumicome of the present specimen usually measures 

 50/x in diameter and occurs abundantly in the subgastral region, as 

 well as in the choanosome. 



Genus HYALASCUS Ijima, 1896 



HYALASCUS ATTENUATUS, new species 



FiGXJBE 7 ; Plate 6, Figure 5 



• 



This new species is represented by two specimens. In specimen A 

 (holotype, U.S.N.M. No. 22014), the body shows a vaselike, or some- 

 what barrellike, appearance. The height is 48 mm and the breadth 

 45 mm near the basal region (the attachment base is torn off, so that 

 it can not be measured), and 40 mm above just under the oscular 

 edge. The wall is moderately thick, 3 mm to 4 mm in the middle of 

 the entire stock, and becomes gradually thinner toward the oscular 

 margin. The osculum is comparatively large and circular, measur- 

 ing 30 mm in diameter. The diactinic prostalia are confined to the 

 oscular edge and to the superior regions of the entire stock. The 

 marginalia generally project straight upward to a length of 5 mm 

 to 10 mm. 



Table 18. — Record of specimens of Hyalascus attenuatus 



