282 ART. 7. 1. IJIMA : HEXACTINELLIDA, IV. 



and deep. On sections of tlie wall it is easy to make out that 

 those of the two systems alternate (fig, 12). 



Spiculation. 



The principal 'pnrenchymalia are slender bow-like oxydiactins, 

 reaching up to 24 mm. length and 132/^ in thickness at the 

 middle. The gradually tapering rays are subtermina.lly more or 

 less rough. Of the more slender parenchymalia I see no points 

 worth special mention. 



The hypodermalia consist of large or moderately large oxy- 

 pentactins with paratropal paratangentials which may reach 12 

 mm. in length and about do /^ in thickness at base. The shaft, 

 up to 15 mm. in length, is always the longest of all the rays ; it is 

 smooth except at the end which is somewhat rougli. The paratan- 

 gentials are likewise smooth in the incompletely developed state 

 of the spicule, but finally acquire the spiny armature characteristic 

 of all Pvhahdocalyptus species. The stout conical spines occur here 

 in a rather irregular distribution — at any rate, not strictly in two 

 lateral rows — at intervals varying from 70 n to 200 //. Those 

 situated on the basal parts of the rays may be 80/^ long, springing 

 at first vertically and then becoming more or less bent in an in- 

 definite direction. Towards the end of the rays they become 

 shorter and more slender, being pointed obliquely away from the 

 spicular center. Exactly as I have enunciated under R. victor 

 (p. 243), the hypodermalia occur in close groups of two or more 

 — frequently as many as eight or nine, — the paratangential heads 

 in each group forming hypodermally an irregularly radiate system 



