1887.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 4^3 



The aetinostome is relatively large. The adambulacral spines form 

 a single row ou each side of the ambulacral furrows, becoming reduced 

 to single rows between adjacent ambulacra, at one-fifth to oue-fourth 

 the length of the furrows from the aetinostome. These spines are com- 

 paratively large. Beginning at the aetinostome, they are generally 

 slender and acute, but where separated into two rows they form close, 

 alternating series of large and small spines, the former, except in young 

 specimens, usually stout and of uniform diameter throughout, but vary- 

 ing considerably in shape ; the latter very small, crowded inwards 

 toward the furrow, often inclining in the same direction, and mainly" 

 limited to the outer halt of the furrows. 



Between the adambulacral spines and the first abactiual row, there 

 are generally, on each side of the rays, four longitudinal rows of spines, 

 which are not, however, always regularly arranged. The three lower 

 rows follow closely after the adambulacral row, while the fourth row is 

 about midway between the former and the first abactiual row. The 

 spines of the lower rows partake of the characters of the adambulacral 

 spines, but are generally stouter, and in large specimens are often ex- 

 panded and compressed at the ends. The spines of the upper lateral 

 row are intermediate in character between those of the lower rows and 

 the abactiual spines. The lower ventral rows extend inward toward 

 the aetinostome one-half the length of the ambulacral grooves or slightly 

 more. 



There is great variation in the size, shape, and number of the spines 

 of the actinal surface and they afford no specific characters. In some 

 of the s})ecimeus they are mostly stout, more or less enlarged at the 

 ends, and blunt, flattened, or slightly bifid ; in others they are more 

 slender, tapering and acute. In the former instance they are generally 

 closely crowded, in the latter more widely separated. The distinguish- 

 ing characters are mainly those afforded by the abactiual surface and 

 the length of the free rays. 



RECORD OF SPECIMENS IN THE COLLECTION. 



Lower California : 



About 4U0 iiiile« south of the boundary hue between the United States and 

 Mexico; C. H. Townseud, ISSo (10036,10998). 



Asuncion Ishiud (3641). 



Cape St. Lucas; John Xautus, type (2017). 

 Mexico : 



West coast (3084, 15921). 



Mazatlau; A. Forrer (10026). 



Heliaster Cumiugii Gray. 



A8terias\Heliaster) Cumingii Gray, Ann. and Mag. Nat. Hist., vi, p. ISO, 1840. 

 Heliaster CumingiiY evviW, Trans. Connecticut Acad. Arts and Sci., i, part 2, 

 1867-1871, pp. 291, 333, 334, 344. 

 This species corresponds most nearly with H. microhrachia in the pro- 

 portionate length of the free rays, but differs from it and from all the 



