412 BULLETIN 82, tJNITED STATES NATIONAL MUSEUM 



are given ofif only on the inner or adradial side of the arm trunks, while in Comaster 

 they arise first on one side and then on the other. 



The number of arms varies from 20 in C. tenella to 160 or more in C. multibra- 

 chiata and about the same number in C. multifida. In C. multifida the number of 

 arms seems to vary within rather wide limits, but in the other species it is remark- 

 ably constant. 



The proximal pinnules are small and very slender, with abruptly differentiated 

 terminal combs usually composed of relatively few very large teeth which are com- 

 monly, in preserved specimens, rolled into a ball. Terminal combs are not confined 

 to the proximal pinnules, but are found at intervals on the middle and distal pinnules. 

 This distribution of terminal combs is not confined, however, to Comaster, though 

 elsewhere it is confined to individual variants in certain species. 



Of the 12 included species, 9 invariably possess well-developed and more or less 

 numerous cirri, while in 3 — one very large, one of medium size, and one small — 

 the centrodorsal is wholly without cu-ri and is reduced to a small stellate plate lying 

 within the radial pentagon. 



The several species of Comaster are undoubtedly much more common than would 

 appear from the records. They are all extremely brittle, and in the majority of the 

 individuals collected the proximal syzygies break through immediately after, or even 

 during, capture, rendering them, if taken in the usual way, scarcely worth the trouble 

 of preserving. 



KEY TO THE SPECIES IN THE GENUS COMASTER 



•o'. Cirri absent; or if any cirri are present they are weak and poorly developed and are irregularly 



distributed about the periphery of the much-reduced centrodorsal. 



b'. Size usually large; division series stout and massive; no black mediodorsal line; 45-130, but 



usually more than 80, arms; interbrachial perisome usually heavily plated (Singapore to 



northwestern Australia, New Guinea, New Britain, and the Fiji, Gilbert, and Philippine 



Islands; 0-91 meters)..- multifida, p. 413. 



b'. Size smaller; division series more slender; a conspicuous black mediodorsal line; no inter- 

 brachial plating, 

 c'. Size moderate; more than 40 (40-80, usually 40-60) arms (Maldive Islands to New Britain, 



Fiji, and the Macclesfield Bank; 0-55 meters) gracilis, p. 430. 



c'. Small and exceedingly slender and delicate; less than .40 arms (Sunda Islands to northern 



Australia and the Philippines; 24[?9]-216 meters) minima, p. 435. 



o^. Cirri present, well developed, and occurring in an uninterrupted marginal row or rows. 



b'. Arms 140-160 in number; cirri numerous, large and stout, with 13-16 segments (Andaman 

 and Lesser Sunda Islands to the Philippines; 31[?9]-55 [?538] meters) multibrachiata, p. 437. 

 6^. Not more than 65 arms. 

 c'. More than 40 arms. 



d'. Cirri short and stout, their length not more than one-tenth of the arm length; longest 



cirrus segments not more than three times as long as the median width; antepenultimate 



segment never longer than broad, and penultimate segment broader than long. 



e'. Cirrus segments 8-11, the longest (third) three times as long as the median width; 



those following decrease in length, so that the antepenultimate is about as long as 



broad and the penultimate is slightly broader than long; the fourth and following 



have slight dorsal processes; arms 37-63 in number, 90 mm. long (Lesser Sunda 



Islands to the Philippines; 35[?27]-106 meters) fruticosus, p. 440. 



e^ Cirrus segments 12-13, the longest (third-fifth) half again as long as broad, or at most 

 only slightly longer; seventh and following with slightly everted distal dorsal ends; 

 ninth or tenth and following broader than long; arms 60 in number, 150 mm. long 

 (China; Singapore) schiinoTi, p. 443. 



