No. IX. ECHINODERMATA. 271 



in some cases at right angles, to the ambulacral series ; 

 whilst midway between the combs and the margin of the 

 ray are three or four small spines (not sufficient to form a 

 paxilla proper), which stand quite isolated and only extend 

 about one third of the distance from the mouth to the tip of 

 the ray. The madreporiform tubercle is excentral and situated 

 at about one-third the distance from the centre to the margin 

 of the disk. The mouth-plates are large and broad, the mar- 

 ginal spines interlocking with one another. 



Only two specimens were obtained by Captain Feilden, the 

 largest of which measures 65 millims. in its greatest diameter, 

 and 21 millims. across the disk ; the arms at the base are 

 13 millims. broad. 



Pteraster militaris (0. F. M.), Miiller and Troschel. 



Coll. Hart : Dobbin Bay, 30 fms. 



This starfish is readily distinguished from its congeners 

 and the majority of other asteroids by the singular fin-like 

 margin surrounding the arms, by the membranous skin whicli 

 is spread over the upper surface, as well as by the series of 

 webbed spines which stand, in transverse ranges like fans, by 

 the side of the ambulacral furrow. 



The form of the animal is pentagonal, the upper contour 

 of the body high and arched, and the underside flat. Propor- 

 tion of disk-radius to arm-radius 1:2. Each interambulacral 

 plate is furnished with five or six long spines, which are con- 

 nected together by a membrane into a webbed comb placed 

 transversely to the ambulacral furrow. The outward spine of 

 each comb is double the length of the others, and extends 

 about half its length beyond the edge of the ray. These long 

 spines are also united to one another by a connecting tissue, 

 and thus form the fin-like fringe which surrounds the entire 

 starfish. The ambulacral spines forming the fan-like comb 

 are nearly equal in length, the middle ones being slightly 

 longer. 



The body-skeleton is composed of a calcareous network, 



