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 jyapposa, Linck, De Stellis mariniy, p. 43. 



Asterias helianthoides, Pennant, Brit. Zool. iv. p. 06. no. 72. 



A. j^apposa, Fabricius, Fauna Gronlandica, p. .369. 



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



? A. alboverrucosa, id. ibid. 



Stelhnia j:apposa, Agassiz, Prodr. Monogr. Rad., Soc. Sc. Nat. Neuf- 



chatel, vol. i. p. 191. 

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

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



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



Coll. Feiiden : 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. 

 Llitken 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 tlie 

 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 Avaters, 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 known as 

 Aaterias ewt/eca, Linn., and yl. p«;//Kwa, Fabr. (Linck). The morpholo- 

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

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

 fore, Forbes's Solaster to his own tj'pe (-S'. endeca), MiiUer and Troschel's 

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

 naturally assigned to the Asterias papposa type, Gray's designation Poli/- 

 asfer having been appropriated by Ehrenberg (Poli/asten'as) at an earlier 

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

 ken sn far back as 18o7. {Cf. Vidensk. Meddelelser, l8o7, p. 3o!) 



t Vidensk. Meddelelser for 1857, p. 40. 



