leucopsacid.t:. 33 



from it. For the present I consider it preferable to include all 

 the four genera in the Leucopsacidie, which may then be 

 diagnosed as follo\YS : 



Lyssacine Hexasteropliora of tliick-walled, cup-like 

 or ovoid body; sometimes stalked; firmly attached by 

 base (? or rooted by basal spicules). Dermal skeleton 

 composed as a rule of moderately large pentactins 

 with the unpaired ray directed proximad; hypo- 

 dermalia not distinguishable. Hexasters represented 

 mainly by discohexasters (no oxyhexaster). 



A key to the genera and species, wliich should also show 

 in a way the structural peculiarities of each, may properly be 

 appended here. 



II. — With hexactinose forms among the discohexasters. Gastralia lioxactinic, snnilar to 



parenchymal hexactlns. Sponge-body small Leucopsacns. 



«1. — Other discohexasters with terminals in a distinct group to each principal. Paren- 

 chymal hexactin with straight rays. Bodystalked 



■. Leucopsucus orthndocua. (Sagami Sea). 



/y^— Other discohexasters generally .spherical in shape. Parenchymal hexactin with 



more or less bent rays. Not stalked... LcucopMcus scoUodocm. (Sagami Sea). 



h. — Without hexactinose discohexasters. Sponge-body of a considerable size. 



c^. — The larger discohexaster with terminal prongs arranged in a whorl like anchor- 

 teeth. Gastralia hexactins Chaunoplectella. 



a". — Dermalia of not only pentactins but also other forms without distally project- 

 ing rays. Discohexaster may be as large as to measure 250-400 y. in diameter. 

 Small and delicate sigmatocomes present on the tip of the outstanding ray 



of canalaria Chaunoplectella cavernosa. (Sagami Sea). 



Z(-.— Dermalia always pentactins, some of which have paratangentials sparingly 

 supplied with bent spines on the outer surface. Discohexaster not larger than 



114 ;j. diameter. Sigmatocome not found 



Ouiunopledella spinifera. (Sagami Sea). 



f^.— The only or the larger kind of discohexaster with convex terminal disc, the 

 margin of which is serrated. 

 C-. — With aspidoplumicome. Gastralia hexactinic. Paratangentials of dermalia 



with curved spines laterally. Body stalked 



Caulocalyx. — C. lener. (W. of Tristan d'Acunha). 



