CHAP, iv.] THE CRUISES OF THE < PORCUPINE* ] 51 



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 bear 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 ambulacral 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 ambulacral 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 ambu 

 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, 

 with sometimes a rudiment of a second attached to 

 it in a gelatinous sheath, which makes it pro 

 bable that it is an abortive pedicellaria. Prom 

 this character, which is one which cannot escape 

 observation, I have called the species ' vexillifer.' 

 I know no star-fish in which the ambulacral grooves 

 are so wide and the ambulacral 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 ambulacral tubes, which when the animal 



