ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER. 



51 



form, while others verge onto an arcuate pentagonal shape. Again, one extreme 

 has fairly massive superomarginals, wliicli are large up to the tip of the very blunt 

 ray, while in the other extreme, the upper marginals are more numerous and rela- 

 tively smaller, and the tip of the ray is not so blunt. The latter form is not so 

 numerous as the first, wliich is "typical." The effect of tliis difference of shape 

 on the relative dimensions is shown in the following table: 



Table showing effect of shape on relative dimensions in Leptychaster anomalus. 



The number of spinelets on the outer half of the adambulacral plates (i. e., on 

 actinal face) varies slightly, and they are a trifle longer and slenderer in some indi- 

 viduals than in others. The tip of the ray in tliis species is rounded and blunt, 

 while it is sharp in pacijicus. Tliis, with the fewer and more transversely placed 

 iuferomarginal jdates of anomalus, will serve to <iistinguish the longer rayed indi- 

 viduals from pacijicus. Variation witliin narrow limits occurs in the size of the 

 paxiUffi, in general the examples ^\-ith more massive marginals having the larger 

 paxillse. The greatest difference in general facies is caused, however, by the varia- 

 tion in size of marginals referred to above. A slight difference in width causes a 

 varj-ing amount of encroachment upon the abactinal paxillar area. In general the 

 shorter armed individuals have \vider and more massive marginal plates, but tins is 

 not invariably the case. The extreme variants in proportions are found at the 

 same station. 



Young. — The smallest specimen (station 4538) measures R = S mm., r = 6 mm.; 

 rays broad, stout, blunt, with seven rather massive superomarginals, wliich are 

 larger relatively' than in adults. Paxillte with nine or ten peripheral and two 

 to five central spinelets; adambulacral plates vnth four furrow spines. Terminal 

 plate small. Tliis species has much larger marginal plates than erpial sized Pseu- 

 darchaster pusillus, and the latter species has very large terminal plates ami spiny 

 inferomarginals, so that there is no danger of confusing the two forms in a super- 

 ficial examination. 



Type.— Cut. No. 21926, U.S.N.M. 



Type-locality. — .<4Ztoross station 3.310, vicinity of XTnalaska, Alaska, 58 fathoms, 

 on fine dark sand ami mud. 



Distribution. — Bering Sea (vicinity of Pribilof Islands and west of St. Paul) 

 to southeast Alaska, and off Monterey Bay, CaUfornia; on the .(Vsiatic side to the 

 Sea of Japan. Bathymetrical range, 32 to 688 fathoms in Bering Sea and northern 

 part of range, to 871 fathoms off Monterey Bay. Found on fine gray or black 

 sand, green mud, or on pebbles. 



