140 APvT. 7. — I. IJIMA: HEXACTINELLIDA, IV. 



This genus, as originally established by F, E. Schulze in 

 the Challenger Report, included, besides A. cactus, two other 

 species that were called A. grossularia and A. dubius ; neither 

 of these however possesses discoctasters and hence can not be 

 placed under the Acanthascinte. The former has since been 

 declared by the same writer ('97, p. ô 37) to represent merely a 

 young specimen of liossella antarctica C^vrtek, Avhile the latter 

 was recognized to be a species which should properly be called 

 Rossella dubia (F. E. Sch.). Subse(_j[uently in '98 (p. 55) I 

 described A. alani from the Sagami Sea and in '99 (p. 45) F. 

 E. Schulze put forth his A. plate'i from the Californian coast 

 (E. of St. Diego, 572 m.). Accordingly, tlie genus as it now 

 stands, comprises three species, the difierential characters of which 

 may be gleaned from the following key : 



«. — Dermalia, predominantly stauractins, occasiüiuil]y peiitacliiis ; gastralia, iDc^lly peutaciiu.*, 

 sometimes stauractins. OxyhexasttT, yo-l.)2 ;j. dia. DiKcot'tasttT, 10()-300 ]i. dia. 



Microdiscohexaster, lo-^Ö;;. dia \. cadiix F. E. ScH. 



b. — Dermalia, predominantly pcntactins, iisunlly witli a Unoli-like rudiment of the distal 

 sixth ray ; gastralia, liexactins. 

 a'. — Oxyhexaster, 1Ü0-1.">U ;j. dia. L>iscüctaster, llîO-JÔO [j. dia. Mierodiscohexaster, at 



most 20 [J. dia A. platei F. E. Sch. 



6'. — Oxyhexaster, 144-19(1 a dia. Diseoctaster, loti-2"J0 a dia. Microdiscohexaster, 30- 

 35 u dia A. aani Ij. 



ACANTHASCUS CACTUS F. E. Sch. 

 ri. XL, ligs. 10-22 and PJ. XII. 



Acaidhascas cactus. F. E. Schulze, '86, p. 49. '87 (!), p. 

 148; PI. LVII., figs. 1-7. '97, p. -351.— Ijima, '97, p. 48. 



