134 



BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



The first six plates usually have but one spine. The (irst plate is longer than the 

 succeeding plates 



The actinostome is small and sunken as is usually the case when the adoral 

 carina is narrow. The mouth plates, at the sutural margin adjacent to the first 

 adambulacral plate, are produced into a sort of flange so that the combined pair 

 is aere conspicuously broader than the first pair of adambulacral plates. This char- 

 acter is less pronounced in some varieties. Each mouth plate has three spines, a 

 very short one close to the actinostome, and usually bent over the beginning of the 

 radial nerve; a second, about 50 per cent longer, stands above it (as viewed from 

 below); and a suboral, similar to tho first adambulacral spine, near the outer margin 

 of the plate. 



The abactinal papular areas, except for a fairly regular series ad j aces t to the 

 superomarginals, are quite irregular in form and arrangement, and variable in num- 

 ber and size. Probably three or four papulae to an area would be an average. In 

 the intermarginal areas there are three or four proximally, and in the actinal, one 

 to three. The numbers vary so with age that they afford no taxonomic ammunition. 



Crossed pedicellariae occur rather sparsely on the sheaths of the abactinal spines 

 and in dried specimens at the base of the spines; in rather scanty wreaths around 

 the base of the superomarginal spines, and as clusters or half wreaths on the outer 

 side of the inferomarginal and adambulacral spines. 



Straight pedicellariae: The large lateral and actinal straight pedicellariae afford 

 the easiest means of distinguishing multispina from alaskensis. Good-sized ovate 

 pedicellariae are present in the supramarginal, intermarginal, and actinal inter- 

 brachial channels; and also sometimes in the actinal channel, and less often on a few 

 of the proximal inferomarginal and actinal spines. Smaller ones of the same sort 

 are sometimes sparsely scattered on the dorsolateral plates. All are broadly ovate 

 as seen from the side, but the back of each jaw is narrower than the height, and tapers 

 slightly. The breadth increases gradually in specimens from more northern localities, 

 until in typical alaskensis from Unalaska and the Aleutian Islands, the jaw is broader 

 than high in well developed specimens, and the whole pedicellaria is relatively larger 

 and heavier than in southern examples. (PI. 48, fig. 4.) The pedicellariae have a 

 few denticulations at the jaw tip. Other smaller, broadly lanceolate, ovate, or 

 subtriangular pedicellariae are present on the furrow margin, furrow spines (along 

 with crossed pedicellariae), and oral spines. 



Type.— Cat. No. E 1503, U.S.N.M. 



Type locality. — Wrangell, Alaska. 



Distribution. — Southeast Alaska to northern Vancouver Island. 



Specimens examined. — Seventeen. 



Specimens of Leptasterias alaske?isis multispina examined 



