the Echinodermata of the Arctic Expedition. 457 



Franklin-Pierce Bay, and were quite young individuals, the 

 largest measuring 16 millims. in its largest diameter. A 

 much finer example was dredged at Proven on the outward 

 journey, in which the diameters of rays and disk were respec- 

 tively 30 millims. and 6 millims. 



Crossaster papposus (Linck), Miiller and Troschel*. 



Triskaidecactis papposa, Linck, De Stellis marinis, p. 43. 



Asterias helianthoides, Pennant, Brit. Zool. iv. p. 66. no. 72. 



A. papposa, Fabricius, Fauna Gronlandica, p. 369. 



A. affinis, Brandt, Act. Acad. St. Petersb. 1834, p. 272. 



? A. albovernicosa, id. ibid. 



Stellmiia papposa, Agassiz, Prodr. Monogr. Had., Soc. So. Nat. Neuf- 



chatel, vol. i. p. 191. 

 Solaster papjjosa, Forbes (1839), Mem. Werner. Soc. vol. viii. p. 121. 

 Crossaster papposus, Miiller & Troscbel (1840), Wiegmann's Archiv, 



iv. pt. 1, p. 183 ; Verrill, Proc. Boston Soc. Nat. Hist. vol. x. p. 334. 



Coll. Feilden : Discovery Bay, 25 fms., hard bottom ; 

 Cape Fraser, 80 fms. ; Franklin-Pierce Bay, 15 fms., bottom- 

 temperature 29°*5 Fahr. 



Coll. Hart : Franklin-Pierce Bay, 13-15 fms. 



In the " Oversigt over Gronlands Echinodermer," Dr. 

 LUtken records f that amongst the specimens of C. papposus 

 which he had examined there occurred only one example of 

 the ten-armed variety, those with twelve arms being the 

 most common. 



All the specimens of this collection are ten-armed, with the 

 exception of one small and very young example having nine. 

 Its greatest diameter is only 18 millims. 



When compared with series of similar size from more tem- 

 perate waters, the polar specimens are characterized by finer 

 arms, fewer spine- clusters (bearing fewer but very much 

 longer spinelets), the spine-clusters more widely separated 

 from one another, and the ventral spaces almost naked. 

 These points are so striking in some individuals that at first 

 sight one is tempted to consider that we have here a well- 

 marked variety of this almost cosmopolitan starfish. Careful 



* The genus Solaster of Forbes included the two starfishes knovra as 

 Asterias endeca, Linn., and A. papposa, Fabr. (Linck). The morpholo- 

 gical differences of these forms are such, hovrever, as to necessitate their 

 being regarded as representatives of two distinct genera. Confining, there- 

 fore, Forbes's Solaster to his own type (S. endeca), MliUer and Troschel's 

 genus Crossaster (synonym of Solaster, Forbes, published a year later) is 

 naturally assigned to the Asterias jiapposa type, Gray's designation Polt/- 

 aster having been appropriated by Ehrenberg (Polyasterias) at an earlier 

 date. The propriety of^ the above limitation was suggested by Dr. Liit- 

 ken so far back as 1857. (Cf. Vidensk. Meddelelser, 1857, p. 35.) 



t Vidensk. Meddelelser for 1867, p. 40. 



