CHAP. iv.J THE CRUISF.S OF THE ' PORCUFJNE' 151 



owing to the position and size of the marginal plates, 

 which run up nearly vertically from the side of the 

 unusually wide amhulacral groove till they meet the 

 edge of the perisom of the dorsal surface. The mar- 

 ginal plates are thickly covered with rounded scales 

 and hear three rows of spines — one at the upper edge 

 (and this series in combination form a fringe round 

 the dorsal surface of the star-fish), one near the centre, 

 and one a little farther down towards the ventral 

 edge. The amhulacral groove is bordered by ob- 

 liquely placed combs of spines, short towards the 

 apex and centre of the arm, but becoming longer 

 towards its base, and forming at the re-entering 

 angles between the amhulacral grooves large sin- 

 gularly beautiful pads ; each plate bearing a double 

 row of spines, and each spine having a second short 

 spine or scale on the end, an arrangement which 

 adds greatly to the richness of the bordering. The 

 inner spine of each comb on the side of the amhu- 

 lacral groove is longer than the others, and bears 

 on the end a little oblong calcareous plate usually 

 hanging from it somewhat obliquely like a flag, 

 Avith sometimes a rudiment of a second attached to 

 it in a gelatinous sheath, which makes it pro- 

 bable that it is an abortive pedicellaria. From 

 this character, which is one which cannot escape 

 observation, I have called the species ' vexilli/er.' 

 I know no star-fish in which the amhulacral grooves 

 are so wide and the ambulacra! tubes so large in pro- 

 portion to the size of the animal as in this species. 

 The dorsal perisom is closely covered with rosette-like 

 paxillae. The colour is a pale rose, with a tinge of 

 buff. The amhulacral tubes, which when the animal 



