150 ART. 7. — T. IJIMA I HËXACTINELLIDA, IV. 



Dermalia predominantly stauractins, rough all over, nearly 

 plane or sliglitly arched so as to be convex on the outer side 

 (PI. XII., fig. 23). Axial length, 200-350 /A Eays perceptibly 

 tapering towards the rounded tip or nearly uniformly thick ; 

 sometimes slightly swollen at the ends. Thickness at their middle, 

 Sh y- on an average. The quadrate meshes formed by mutual 

 apposition of the rays of separate derraalia measure on an average 

 165 !'■ in length of sides. 



Occasionally among the dermalia there occur peutactinic 

 forms in which the proximally directed, unjwired ray is somewhat 

 shorter than, or nearly equally as long as, tlie paratangentials. 

 They scarcely ever occur on the cones. Under exceptional 

 circumstances a stauractin may have one of the rays so 

 shortened that it approaches a tauactin in shape. A few cases 

 of unusually small, smooth and slender-rayed oxystauractins and 

 oxypentactins that I have seen I hold to be dermalia in an in- 

 complete state of development. 



Gastralia rough pentactins, in which the unpaired ray is 

 directed distad (PL XII., fig. 24) ; occasionally stauractins. They 

 are (juite like the dermaliii, though perhaps on the whole slightly 

 smaller. As before mentioned they are never so numerous as to 

 form a continnous gastral lacework, occurring, as they do, in 

 widely scattered distribution on the hypogastral strands (see PI. 

 XII., fig. 35). 



Oxyhexasters, 00-152// in diameter (120/^ on an average). 

 Those occurring in abundance in the choanosome as well as in 

 the endosome (PL XII., figs. 29-32) have mostly exceedingly 

 short principals which in many cases may be said to be almost 



