CHAUNOPLECTELLA SPINIFERA. 75 



The hexasters are discoliexasters (PL VI., figs. 3-7) of varied 

 size and appearance, occurring very commonly in the paren- 

 chyma. Of them I may distinguish at least four varieties, which 

 however completely grade over into one another by intermediate 

 forms, so that a sliarp demarcation can not be drawn between 

 them. 



In the first place, there occur, especially abundantly in the 

 peripheral part of the body, small and spherical or nearly spherical 

 forms of discoliexasters, of which fig. o, PI. VI., may be con- 

 sidered a typical representative. It closely resembles the form a 

 of the discoliexasters of Ch. cavernosa (p. Q(S). Diameter, 64-90 /■«. 

 Each principal, which can not be said to be very short, bears a 

 bunch of 5, 6, or more terminals. These are smooth-surfaced and 

 thicken slightly towards the outer end ; they so diverge that the 

 terminal discs in the entire rosette are nearly equidistant from 

 one another. The discs are small, watchglass-like and outwardly 

 convex ; their margin shows 6-8 small teeth. 



Common in the deeper parts is a second variety of disco- 

 liexasters, distinguishable from the first by its larger size and 

 1jy a tendency of the terminals to each principal to form a 

 separate tuft (PI. VI., figs. 4 and 5). Diameter, 90-160 /^ The 

 terminals, smooth and outwardly somewhat thickened, number 6- 

 9 to each principal. The discs at the ends have small marginal 

 teeth, just like those exhibited by the variety first mentioned. 



A third variety of discoliexasters is made up of those which 

 form the largest rosette of the species and in which each long 

 and slender terminal is capped with a disc composed of 4-6, 

 moderately large, recurved prongs arranged in a whorl (PI, IV., 

 fig. 7). In appearance it is very much like those discoliexasters 

 ill Ck. caocrnom, which I have called Form h. Diameter, up 



