ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 77 



ing of the ambulacral ossicles by which alternate pores are squeezed out of line. All 

 degrees of these are found in the Asteriinae. In Ampheraster, two species have a 

 biserial arrangement of tube-feet, even to the base of the ray; the other three have 

 the tube-feet quadriserial in various degrees. In Pedicellaster, Hydrasterias, and 

 Peranaster the tube-feet are strictly biserial. These three genera have a considerable 

 gap between the interradial border of the first postoral pair of adambulacral plates, 

 sometimes even to the intrusion between these plates of the outer end of the combined 

 mouth plates. In Tarsaster and Ampheraster this first pair of plates is either separated 

 by a muscular symphysis (sometimes fairly broad) or else the adoral corners are in 

 close contact. In Ampheraster marianus only the largest specimen has the plates in 

 contact; in others they are separated. In A. atactus the plates are obviously in con- 

 tact. In the large A. hyperoncus the plates are well separated. This feature thus runs 

 the gamut from the condition in Pedicellaster nearly to that of the least specialized 

 Asteriinae, apparently in correlation with the structure of the ambulacral plates which 

 are quite Pedicellaster-\ike in A. hyperoncus and not at all so in marianus aud atactus. 



KEY TO THE KNOWN SPECIES OF TAESASTEB 



a 1 . Adambulacral plates diplacanthid, or the first few triplacanthid; abactinal crossed pedicellariae 

 0.26 to 0.32 mm. long. 



6 1 . Abactinal spinelets arranged in transverse series, the carinal and superomarginal plates with 



about 3 spinelets; oral plates each with 3 or more spinelets. 



c 1 . Spinelets cylindrico-conical, robust, erect; dorsolateral plates with 1 or 2 spinelets; adoral 

 adambulacral plates touching by adoral corners; accessory inferomarginal spinelet not 

 well developed; major inferomarginal spine lanceolate, flattened (150 fathoms, north 

 of Admiralty Islands) stoichodes Sladen. 



<?. Spinelets rather slender, tapering, not erect and stubby; dorsolateral plates with more 

 often two or three spinelets; adoral adambulacral plates separated, accessory infero- 

 marginal spine well developed; major inferomarginal spine terete, clavate, in length 

 equal to about 1.2 to 1.5 plates; minor inferomarginal spine equal to or larger than 

 the superomarginal spines alaskanus Fisher. 



6 2 . Abactinal spinelets not in transverse series, the carinal and superomarginal plates with one 



spinelet each; oral plates with two spines each; major inferomarginal spine lanceolate, 

 flattened (1.5 plates in length), the minor, slenderer, shorter, and sharper than the blunt 



superomarginal spinelets galapagcnsis 28 (Ludwig) 



a 2 . Adambulacral plates diplacanthid, sporadically monacanthid, distals largely monacanthid. 

 abactinal crossed pedicellariae about 0.36 to 0.38 mm. long; major inferomarginal spine 

 robust, tapered, blunt, very slightly flattened, in length equal to 1.2 to 1.5 plates; minor 

 inferomarginal spine about two-thirds as long, blunt or pointed, larger than the two or three 

 small subcylindrical or clavate superomarginal spinelets (in transseries) ; abactinal spinelets 

 similar, small (0.55 to 0.65 mm.), subclavate, erect, stubby, one or two on dorsolaterals, 

 three on carinals; dorsolaterals irregularly spaced, not in evident transseries. (Guadeloupe, 



West Indies) fcucicttiaria ■' (Perrier) 



a 3 . Adambulacral plates monacanthid except first 9 or 10 which are diplacanthid; distal plates 

 sporadically diplacanthid or rarely triplacanthid; abactinal crossed pedicellariae about 0.45 

 mm. long; abactinal and marginal spinelets short, very robust, tubercular, subcylindrical; 

 the major inferomarginal spine sublanceolate, somewhat flattened (one plate in length); the 

 minor spine, tubercular, rather smaller than the superomarginal spinelet. 



cocosanus 2S (Ludwig) 



» Sporasterias galapagensis Ludwig, Mem. Mus. Comp. Zool., vol. 32, 1905, p. 240, pi. 34, figs. 202, 203; station 3404, south ot 

 Chatham Island, Galapagos Islands, 385 fathoms, rocks; bottom temperature 43.2 Fahr. 



" Asttrias fascicular!* Perrier, Mem. sur les Etoiles dc Mcr ("Blake"), Nonv. Arch. Mus. d'Uist. Nut., ser. 2, vol. 6, 1884, 

 p 200 pi 3, Guadeloupe, 309 fathoms. Data from type No. 1210. Mus. Comp. Zool. 



' « Sporasteriascocosana Ludwig, Mem. Mus. Comp. ZoSl., vol. 32, 1905, p. 235, pi. 33, flg. 199; pi. 34, figs. 200, 201; station 3370 

 off Cocos Island, 134 fathoms, rocks, shells; bottom temperature 51.8 F. 

 64406—28 6 



