E. KOMEYAMAI. — SPICULAÏION. 261 



111 a large specimen of prostal hexactins the distal (prostal) 

 ray, which is always the longest and the strongest of all the six 

 rays, may be 10 mm. or more in length. The opposite proximal 

 ray is shorter, and shorter still are the four paratangential rays. 

 While the proximal and the paratangential rays are entirely 

 smooth, the prostal ray is, like the coronal ray, beset with short, 

 conical, obliquely outwardly directed prongs (PL X, fig. 10). In 

 many cases, however, it was found smooth on one side — generally 

 the concave side of gently curved shafts. In the smaller prostal 

 hexactins, the above prongs are more weakly and sparsely 

 developed. 



The hexactui-devmalia (PI. X, figs. 14, 15) are also subject 

 to certain variations in regard to the size and proportional length 

 of the rays. In general we may say that the rays are slender, 

 measuring only about 9 /^- in thickness near the base. They are 

 nearly entirely smooth or subterminally obsoletely rough ; the 

 ends are rounded or bluntly pointed. 



The free distal ray varies in length from, say, 120/^ to 

 240/^. It is scarcely distinguishable from the other rays except 

 by its relative shortness or by the fact that it is often slightly 

 less tapering towards the end. The paratangential rays are 

 straight or gently bent and about 300/^ in average length. The 

 proximal ray may be either shorter (fig. 14) or much longer 

 (fig. 15) than the paratangentials. The former is the rule es- 

 pecially with those dermalia in which that ray ends free in the 

 subdermal space, as is the case in such parts of the dermal layer 

 as extend over incurrent apertures. The proximal ray is gene- 

 rally longer — at times twice as long or even longer — than the 

 paratangentials, and the entire spicule thus becomes more or less 



