42 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



Heliaster helianthus (Lamarck). 1 



Plate 3, Fig. 1 5 Plate 7, Figs. 1-7. 



Tournesol Davila, 1767. 



Asterias helianthus Lamarck, 1816. 



Stellonia helianthus Agassiz, 1835. 



Asteracanthion Helianthus Miiller and Troschel, 1842. 



Heliaster helianthus Dujardin and Hupe, 1862. 



Description. — Rays 30— 40, averaging (51 individuals) 34.8; about 35 (29—43) per 

 cent of ray, free. R=75— 150 rum. ; r=45— 90 mm. Breadth of ray at base, 8—15 

 mm. R=7— 9 br. Rays more or less flattened both aetinally and abactinally, angu- 

 lar with nearly vertical sides, commonly tapering but often abruptly blunt-pointed, 

 becoming more nearly terete near tip. Disc large, little or not at all elevated 

 above base of rays; in a specimen with R=150 mm. the vertical diameter is only 

 about 30 mm. 2 Abactinal surface covered with a stout, reticulated skeleton having 

 rather small meshes. Skeletal plates with numerous spines of variable size, form, 

 and arrangement. There are usually three well-marked series on each ray and 

 these continue inward onto the disc far beyond the base of the ray ; the median row 

 is the most conspicuous and includes numerous clusters of more or less capitate 

 spines ; the lateral rows contain fewer spines, commonly arranged in a single series, 

 which may be larger or smaller, and more or less capitate, than those in the median 

 row. The lateral rows are nearly parallel with each other and remain separate, 

 so that the median series is also present proximally. On the central part of the 

 disc, the prominent and usually capitate spines do not show a serial arrangement 

 but they are commonly grouped in more or less irregular, short lines, which 

 form a sort of imperfect reticulation. In some specimens this network is quite 

 distinct, the meshes being three or four millimeters in diameter and each side of 

 a mesh consisting of a crowded single series of from three to seven spines. In 

 other specimens no reticulation is evident, the spines being irregularly scat- 

 tered, although here and there a few tend to form a crowded, linear series. Speci- 

 mens sometimes occur in which no arrangement of the abactinal spines is 

 evident even on the rays, but they appear to be scattered irregularly everywhere. 

 Besides the conspicuous spines, smaller and more slender ones frequently occur 

 abactinally, and pedicellariae, chiefly of the forcipate type, are more or less abun- 

 dant, especially near the tips of the rays, while papulae occur everywhere. — Sides 

 of rays with three or four longitudinal series of spines which are usually very 



1 No attempt is made to give complete synonymies of the seven species, as that 

 would involve a virtual repetition of the bibliography already given. Only such 

 names are listed as show some difference from the one originally given or the one 

 herein accepted. It should be noted in passing that Gray never used Heliaster as 

 a generic name and never published it in direct connection with any specific name ; 

 consequently it is not correct to write " Heliaster helianthus (Lam.) Gray "as has 

 often been done ; if two authors are to be referred to, the name should be written 

 as Sladen gives it, " Heliaster helianthus (Lam.) Dujardin and Hupe." 



2 It is useless to attempt to distinguish externally the true limits of the disc, and 

 the term is used in these descriptions to include the fused basal portion of the rays. 



