KM) BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



from one to a plate to a crowded group of five or six, and the size, from slightly to 

 conspicuously larger than the dorsolaterals. The dorsolateral spinelets vary from 

 one incomplete longiseries to the equivalent of throe, such specimens being in fact 

 nothing more than examples of nitida with grouped carina! and spaced dorsolateral 

 spinelets. 



Shumagin Islands: Largest specimen, R 47 mm., has one or two supermarginal 

 spines, rather numerous dorsolaterals, and not very prominent acervate carinals. 

 The five specimens from the Shumagins suggest young acervata, but are not. 



Chernoffski Bay, Uhalaska: A specimen (47 R mm.) has rather narrow, arched 

 rays and proximally three or four supermarginal spines, in an arcuate vertical comb. 



Unalaska, Alaska: In addition to three small typical examples there are nine 

 intermediates some of which may be called acervate examples of nitida. The spines 

 of the conical groups are not neat and compact as in the St. George Island variety. 

 Supermarginal spines usually two, sometimes one. 



St. George Island, Pribilof Islands: These belong really to a subforma of nitida 

 rather than to forma dispar. Along the carinal ridge (the ray being well arched) is 

 a zigzag series of conspicuous, convex, compact groups of 8 to 12 unequal, but en- 

 larged, close-set spines; dorsolateral spines numerous, superomarginals two or three. 

 (See under f. nitida, pi. 49, fig. 4.) 



Adakh Island, Andreanof Group, Aleutian Islands: A specimen resembles the 

 St. George examples but the groups are smaller; the superomarginals two; R 73 mm. 

 There are rather numerous coarse ovate intermarginal straight pedicellariae but they 

 are not of the form nor nearly as large as those of alaskensis. This large specimen may 

 be classified as an acervate specimen of forma nitida, or as dispar with numerous 

 dorsolateral spinelets. One specimen with much fewer dorsolateral spinelets. 



Nazan Bay, Atka: The specimen figured by Verrill (1914, pi. 106, fig. 3) is much 

 smaller than the two recorded here (R 70 and R 65 mm.). In these the carinal spines 

 are prominent and the dorsolaterals well spaced but more numerous than in the 

 example from Attn described above. Superomarginals two. Intermarginal straight 

 pedicellariae smaller than in the Adakh example. 



Attn Island: A small example with two supermarginal spines connects the 

 extreme type form, from Chickagoff Harbor, Attu, with what might be called the 

 intermediate variety, of which there is one specimen (in addition to the large extreme 

 form described) collected at the same locality. 



Remarks. — The following differences may be. observed between approximately 

 equal-sized specimens of f. dispar and Leptasterias polaris acervata f. acervata; examples 

 of acervata with R 50 to 70 mm.; of dispar with R 66 mm. Acervata has a smaller 

 disk, and the rays arc slenderer, especially at the base (R = 4.5 to 5 r). The dorsolat- 

 eral spines are much more numerous, and a certain number of them are enlarged (as 

 are the carinals) and form spaced, scattered clumps which are strongly convex. The 

 supramarginal and intermarginal channels are narrow, the former being not at all 

 conspicuous, as in dispar. In typical dispar the supermarginal plates are more 

 prominent, the spines being a little longer. Small specimens of acervata (R 22 to 27 

 mm.) do not resemble equal-sized typical dispar but they do resemble some of the 

 intermediate stages of dispar from Unalaska. The latter lack the dorsolateral 

 convex groups of acervate spines. 



