ROSY FEATHER-STAR. 



cate, so that as the two branches of each arm are very 

 long-, and the undivided part extremely short, the animal 

 appears to be ten-armed. These arms are pinnated with 

 single pinna?, each of which bears a membranous expansion 

 and other organs, all which parts we must now examine 

 in detail. 



1. The cup-shaped base is very convex on one side, and 

 deeply concave on the other. The convex part consists of 

 a somewhat pentangular disk or true base, and five sides 

 or surfaces. The disk is smooth, but the sides are punc- 

 tate, with concave hexagonal impressions, the largest of 

 which are lowest. These are the sockets of the filaments, 

 which vary in number according to the age of the animal, 

 being from twenty to thirty in one full grown. There 

 are also perforations on these punctate sides, which seem 

 to be the openings of canals branching out from five main 

 canals, which proceed from near the bottom of the con- 

 cavity or cup. The disk is imperforate ; but when we 

 make a section of the cup, we find a funnel-shaped cavity, 

 which extends very nearly to the surface of the centre of 

 the disk. The concavity of the cup presents ten canali- 

 cnlated radiating ribs, five of which are more depressed 

 than the others. 



2. The filaments, jointed appendages, or simple arms, 

 with which the convexity of the base is furnished, are 

 calcareous and jointed ; the joints a little concave in the 

 middle, and thickest at each end, so that the articulations 

 have a slightly knotted appearance. These filaments are 

 not all alike ; there are two kinds of them. The larger 

 have fourteen joints, and a small, thick, blunt, curved claw, 

 which is smaller than the joints and has a horny lustre : 

 the smaller filaments have eighteen rough joints, and an 

 almost straight claw, which is larger than the joints pre- 

 ceding it. 



