REPORT ON THE HEXACTINELLIDA. 363 



becular network : — (1) sim^ile oxyhexasters which are always beset with pointed spines ; 

 (2) discohexasters of various sorts, including isolated forms with short principal rays 

 and six to ten long markedly divergent terminals, in some cases strongly developed 

 (PI. CIV. fig. 7), and in others quite thin and delicate (PI. CIV. fig. 5). There is, on 

 the other hand, a very abundant occurrence of discohexasters in which each of the long- 

 principals bears a tuft of six to ten, slightly divergent, fine, moderately long terminals 

 (PI. CIV. fig. 6). Here and there (3) graphiohexasters occur, with short principal rays 

 and very long, extremely delicate, slightly undulating terminals, which form a loose 

 divergent tuft on each principal (PI. CIV. fig. 4). In some places as a support to the 

 dermal membrane of the tubes, moderately strong oxypentacts occur with a hypodermal 

 radial ray, usually somewhat elongated. While the internal portion of their rays is 

 usually smooth, the outer ends are more or less abundantly beset witli pointed tubercles. 

 A rounded-oft' rudiment of a sixth (distal radial) ray is of very frequent occurrence, and of 

 variable size. In structure and size resembling these hypodermalia, hypogastral pentacts 

 occur with their tangential rays in the gastral membrane. On the external limiting 

 membrane of the capsule there is a layer of hypodermal pentacts- which entirely resemble 

 those above described. On the inner surface of the capsule there is in many places no 

 special skeleton, while other regions exhibit a layer of large oxypentacts with toothed 

 ends to the rays, and arranged in contrast to the former pentacts with the radial 

 unpaired ray directed outwards. The strands of tissue between the two parallel limiting 

 lamellse of the capsule contain either no spicules at all, or in certain positions somewhat 

 long straight rough diacts, wdth central swelling, and pointed or slightly rounded toothed 

 extremities. 



