STAEFISHES OF THE PHILIPPINE SEAS. 359 



comb, and when standing upright reaching about half the length of 

 the inner subambulacral spine. Subambulacal spines 2 (3 on first 2 

 plates), in an oblique transverse series, the outer conspicuously the 

 larger and situated adorad of the inner. The outer spine is flattened, 

 untapered, with a rounded or truncate tip, and is slenderer than the 

 adjacent spatulate actinal intermediate spines. The inner spine is 

 slenderer and slightly flattened in a plane oblique to furrow. Near 

 the end of ray the inner spine is subspatulate at tip and a little 

 heavier than the outer. Adorad of the inner spine is usually an up- 

 right pedicellaria with 2 slender, lanceolate, or narrowly spatulate 

 jaws about as long as the furrow spines. Margin of plate bordered 

 bv unequal pinched granules. 



Mouth plates narrow, with 7 furrow and 4 heavier suboral spines in 

 a parallel series. The innermost mouth spine of each jaw is shorter 

 than the next spine. The angle pair of spines is therefore less con- 

 spicuous than usual in this famil}^ 



Madreporic body convex, with fine radiating convoluted striae, 

 situated about two-fifths r from center. 



Tlie dorsal skeleton from the coelomic aspect differs from that of 

 A. truncotus. In the latter the large primary plates are connected by 

 2 slender ossicles end to end, the junction resting on a secondary plate. 

 There are 6 of these double ossicles radiating from each plate, and 

 the triangular meshes of the skeleton thus formed are unusually 

 large. In A. helonotus the primary plates, with some exceptions, are 

 connected by a single ossicle, longer, however, than 1 of the ossicles 

 in A. truncafus. Six of these radiate from each primary plate; the 

 inclosed triangular meshes are smaller than in A. triincatus. It has 

 already been pointed out that the primary plates are more numerous 

 in A. helonotus. 



Tyve.—Q^i. No. 32633, U.S.N.M. 



Type-locality. — Station 5149, off Sirun Island, vicinity of Siasi, 

 Sulu Archipelago, 10 fathoms, coral, shells ; 1 specimen. 



Distribution. — Known only from type-locality. 



Remarks. — ^The chief points of difference between this species and 

 A. tmmcntus have been alluded to in the diagnosis. In trtincatus the 

 abactinal tubercles are much larger, as I have had the opportunity 

 of comparing a small portion of the abactinal surface of A. trunoatus 

 directly with that of A. helonotus., where the secondary tubercles 

 closely fill the interspaces betAveen the primary tubercles. In triin- 

 catus the secondary are less numerous and leave wider interspaces, 

 and are actually larger than the primary tubercles of helonotua. The 

 large size of the terminal supcromarginal, as well as the small size 

 of the other superomarginals, appear to be differences of importance. 

 In A. truncotus there are 9 or 10 inferomarginals, in elegans 9, in 



