70 l;lLLETIN 76, UNITED STATES NATIONAL MUSEUM 



Of the above, two large specimens, No. 39984 and station 3496 are unlike the 

 usual run of acervata. They have much fewer, more widely spaced, larger spines. 

 No 399S-1 abactinally resembles L. Jcatherinae, but has the crossed pedicellariae of 



Ota; station 3490 has a few larger spines here and there and one series of supero- 

 marginals. It may perhaps be a variant of polythda. Both have larger and more 

 widely spaced spines than f. a phelonota . 



Vowng. The smallest specimen has R 8.5 mm. (station 3233) and could not be 

 accurately identified if it were not accompanied by adults. The rays are moderately 

 stout, depressed, and the abactinal spines unequal, comparatively coarse, and rela- 

 tively few. Even at this early age a few spines here and there in the radial region 

 overtop the others and are usually distinguishable by having one to three crossed 

 pedicellariae on their bases. There is one superomarginal spine to a plate and one 

 inferomarginal, a little longer, each with several minor pedicellariae. Adambulacral 

 spines cither one or two, rather irregularly; a few straight pedicellariae scattered 

 along the furrow face. One pair of adambulacral plates meet behind the mouth 

 plates. First two or three tube-feet biserial, then quadriserial in quincunx. Papulae 

 solitary, none actinal, but an intermarginal series present. 



Another example with R 10.5 mm. is essentially the same. 



Small examples with R about 30 mm. show most of the varietal differences of 

 the adult, but in a less accentuated form, since the spines are fewer. There are usually 

 one inferomarginal, one actinal, and either one or two superomarginal series of spines. 

 Sometimes a second inferomarginal spine of smaller size. Crossed pedicellariae are 

 plentiful. These and the absence of large bivalved denticulate intermarginal and 

 supramarginal straight pedicellariae will serve to distinguish young acervata from the 

 closely similar shore form, Leptasterias alasJcensis, found along the Aleutian Chain 

 from Unalaska to Attu and Agattu. 



The specimen figured by Verrill (1914, pi. 106, fig. 3), Nazan Bay, Atka, as young 

 acervata is referable to Leptasterias camtschatica dispar. 



Type. — Cat. No. 1366, U.S.N.M., William Stimpson. The specimen figured by 

 Verrill (1914, pi. 27, figs. 1, 2) is not the type, as stated, but is Cat. No. 1367, 

 U.S.N.M., Arctic Ocean, Captain Rogers. It is, however, practically identical with 

 the type. 



Type locality. — Bering Strait, clean gravelly bottom, 5 to 15 fathoms (Stimpson). 



Distribution . — Forma acervata is found from the Arctic Ocean to Bristol Bay, 

 Bering Sea, Attu Island, and on the Siberian coast to Indian Point. Its known 

 temperature range is slightly higher than that of polytMa, but the temperatures of 

 arctic stations are not known. 



Specimens examined. — Eighty-nine. 



