LEUCOPSACUS SCOLIODOCÜS. 51 



beset with prickles on the surface. The hexactins may be so large 

 as to measure 120/^ in axial leugth and 10/>« in thickness of rays. 

 At places the prickles on the basidictyonal beams are elongated into 

 stout, sharply pointed spines, as much as oO /^ in length. 



As constant hexasters of the species are to be mentioned disc- 

 ohexasters of both the hexactinose and the hexasterous varieties. 



The hexactinose discohexasters (PI. III., figs. 29 and 30) are 

 shaped exactly like those of L. orthodocus. They are of common 

 occurrence everywhere in the body-wall ; only in the specimen 

 (No. 434) from Onigase were they found scantily represented. 

 Axial length, 100-180 /a Number of terminal anchor-teeth, 

 usually 3 or 4, sometimes 5, in a whorl. The limited extent of 

 axial threads in the spicule, as ascertained by special examination, 

 is depicted in fig. 30. 



Of the hexasterous discohexasters, the most constant are the 

 forms shown in PI. 111., figs. 32-34. These are especially 

 abundantly met with in the periphery of the wall. In diameter 

 they commonly measure 70 /^, though sometimes only tis much as 

 46 /^. In the larger discohexaster each very short principal 

 usually bears 8 or more, rough-surfaced, moderately strong-looking 

 terminals, while in the smaller one there may be only 4 terminals 

 to a principal. The small, convex, terminal disc is provided 

 with 5 or more, minute, marginal teeth. The terminals from all 

 the six principals radiate in such a w^ay that the terminal discs 

 are all situated nearly equidistant from one another, the result 

 being the spherical shape of the entire spicule. Here I see 

 another point of difference from L. orthodocus, in which the 

 corresponding discohexaster has the terminals arising from each 

 principal arranged in a separate perianth-like tuft. — As variations 



