58 I. IJIMA : HEXACTINELLIDA. I. 



Key to the Species of Euplectella. 



«• — Tlie parenchyma] principalla of tlie circular and longitudinal skeletal beams are staur- 

 actins. 

 a^. Spicules of the skeletal beams never in fusion. 



«'• Parietal ledges well developed; oscularia of miscellaneous forms 



E. marshalli Ij. (Sagami Sea; Suruga Gulf). 



6*. Parietal ledges little or not at all developed ; oscularia mainly diactins. 



a^. Oxyhexaster with straight terminals, 50-70 [j- in diameter 



E. oweni Herkl. & Maksh. (NW. of Kyüshyü). 



b^. Oxyhexaster with terminal rays bent near the outer end, 75-100 pi in diameter. 



E. curvislellata Ij. (S. of Kyüshü). 



6'. Spicules of the skeletal beams in fusion, at least in the basal region. 



c". Parietal ledges not developed ; all meshes of the skeletal framework with a 



parietal osculum each; oxyhexaster not present 



E. simplex F. E. ScH. (Sea of Bengal). 



d^. Parietal ledges or protuberances well developed ; a number of the meshes of the 

 skeletal framework without parietal^oscula ; oxyhexaster present, 

 c'. Ledges cut up into irregular knobs, flaps, &c.; oscularia chiefly hexactins 



and pentactins E. impevialis Ij. (Sagami Sea; Suruga Gulf). 



d^. Ledges with tolerably sharp continuous edges. 



a*. Ledges low ; without graphiocome...JE'. regcdis F. E. Sch. (Sea of Bengal). 



b*. Ledges prominent ; with grapliiocome...Ê'. a'^pergillum Ovf. (Philippines). 



''. — Tile parenchymal principalia of the circular and longitudinal skeletal beams are all or 



at least partially oxypentactins, or oxyhexactins with one ray directed distally and 



radially. 



c'. The parenchymal principalia are oxyhexactins with a reduced proximal ray. 

 Stauractins may occur in addition. 



c". Distal ray of parenchymal oxyhexactins armed with prongs and conspicuously 

 projecting out of the external surface. Oxyhexaster with short slender principals 



and long terminals E. aspera F. E. Sch. (Indian Ocean). 



/-. Distal ray of parenchymal oxyhexactins smooth, not freely projecting (?) ; oxy- 

 hexaster with moderately long and thick principals and short terminals 



E. cmssklellala F. E. Sch. (Mid-Pacific). 



d'. The parenchymal principalia are smooth oxypentactins with entirely suppressed 

 proximal rays. However, oxyhexactins may occur in addition. 

 g'^. Distal ray of parenchymal oxypentactins reaching to the external surface but 

 not beyond; yet, with outwardly projecting bundles of small thin diactins; no 



oxyliexaster E. nodom F. E. Sen. (Bermudas). 



/('-. Distal ray of parenchymal oxypentactins freely projecting out of tlie external 

 surface. 

 e^. Oxyhexaster represented by clasp-like or sigma-like fibulre (oxydiaster) ; 



oscularia scepter-like monactins E. jovis O. Schm. (W. Indies). 



/'. Eitiier typical oxyhexaster or onychaster present; no fibula;. 



c*. Body tubular, scarcely bellied; spicules nowhere in fusion; oscularia 



rough rod-like diactins E. suherea W. Thoms. (Atlantic). 



d*. Body distinctly bellied; spicules in fusion in certain parts; oscularia 

 unknown F. cucumer Ow. (Seychelles). 



