MUSEUM OF COMPARATIVE ZOOLOGY. 235 



seventeen form the margin, and the rest are arranged in two or three irregu- 

 lar lines. Mouth-shields rather broader than long, of a rounded diamond 

 shape. Under arm-plates covered by a thick skin ; squarish, with rounded 

 corners. Side arm-plates rather small; although, below, they make a well- 

 marked rid^e for the arm-spines. Upper arm-plates much wider than long, 

 six-sided but with much rounded angles; the lateral corners pointed ; length 

 to breadth, near disk, .7 : 1.7. Close to tip of arm, the shape is wholly dif- 

 ferent ; longer than broad, wider without than within, the outer side curved; 

 length to breadth .5 : .4. Disk covered by thick skin which obscures the 

 outline of the radial shields, and nearly hides the scaling. Near the edge 

 are a few scattered spines, about .5 mm. long, stout and conical, and which 

 are more numerous on the. under side. Radial shields quite smooth ; length 

 to breadth 3.5 : 2.5. Arm-spines near the disk, seven; the upper ones 

 short, stout, with a nearly smooth shaft, and a club-shaped end bearing 

 strongly curved thorns ; the lowest one keeps the form of a triple or quad- 

 ruple hook quite to the base of the arm. Lengths, to that of an upper arm- 

 plate, 1.8, 1.9, 1.8, 1, .G, .4, .4, : .7. Close to tip of arm only three spines, 

 of which the uppermost is longest; the lowest is a hook, the other two hav- 

 ing a rounded shaft and about six curved thorns at the end. Tentacle-scales 

 small, scale-like, usually serrated. Color, above, bright indigo, with a 

 darker line along the arm, bounded by a lighter one on either side; below, 

 paler indigo, with a white line along the arm. 



A smaller specimen with disk of G.5 mm. had a thinner skin, so that the 

 various plates were better defined, and the ends of the arm-spines seemed 

 more thorny. In the. interbrachial spaces between the radial shields could 

 be distinguished four irregular radiating rows of oval scales. Below, the 

 short disk-spines were more numerous than in the full grown, and were a lit- 

 tle thorny at their ends. The blue lines along the arms were, continued to 

 the centre of the disk, but were not margined by lighter lines. Under arm- 

 plates thick and conspicuous; squarish, with rounded corners; length to 

 breadth (7th plate) .6 : .G. Chewing apparatus the same as in the adult, 

 except that the oval of small tooth-papillas has only twenty-one, of which 

 eight papilla? form an irregular double or single line. 



Philippines; by Semper. 



Specimens also in Garden of Plants; at Berlin, and at Stockholm. 



Ophiothrix pusilla sp. now 



mate III., Figs. 21 - 30. 



Special Marl;*. — Upper arm-plates swelled, narrow, covering only part of 

 the arm. Side arm-plates with a projecting point running toward the upper 



