ARCTIC SEA TO THE WEST OF GREENLAND. 39 



of a long-armed variety, in which the rays are flatter and more pointed, and the paxillae 

 smaller but more numerous. Examples of a similar form occurred in the collections 

 made during the British Arctic Expedition of 1875-76 ; and there may also be noted in 

 these specimens an increase in the number of lateral paxillary combs concurrent with 

 the greater length of the ray. 



The number of rays is also subject to variation, the presence of ten especially 

 seeming to bear a locational significance. Only one example from Greenland is cited 

 by Liitken ; but amongst the specimens collected in the extreme north by the naturalists 

 of Captain Nares's Expedition (mentioned above) this number of rays was the general 

 rule. 



It would seem probable that the two species established by Brandt under the 

 names of Asterias affinis and A. alboverrucosa should be ranked in the present category, 

 since the characters upon which the specific individuality of these forms is based arc, 

 excepting the number of radii, only those which accompany early phases of growth ; 

 and this fact, together with the small size of the recorded type (disk 1 inch in diam.), 

 would go far to warrant the conclusion that (in the case of affinis at least) Brandt's 

 species is nothing more than the young stage of the northern ten-armed form of 

 C. papposus. The description given in the ' Prodromus Descrip. animalium &c.' is itself 

 so brief, that it furnishes no features upon which a contrary opinion can be maintained; 

 but at the same time the statement should not be lost sight of that the diagnosis was 

 founded not upon an actual specimen, but only upon a drawing by another hand. 

 Obviously, therefore, no great reliance upon the determination can be accorded by, or 

 even be expected of, posterity in such a case. 



In the recently published memoir by MM. Danielssen and Koren on the Echino- 

 dermata of the Norwegian North- Atlantic Expedition*, two specimens of Crossaster are 

 referred to this obscure species of Brandt's (A. affinis) and carefully described (1. c. p. 57). 

 It would seem to us, however, that the details there cited may, with perhaps only a 

 single exception, be shown to occur in forms which can be traced through all the stages 

 of variation up to the undoubted typical C. papposus, and not unfrequently even in 

 British examples of the species. 



One very marked peculiarity, however, is noted in the description above referred 

 to, and which consists in the great number of spinelets present in the series on the 

 furrow side of each adambulacral plate, viz. seven (or even eight rarely) ; whilst in large 

 specimens of C. papposus it is very seldom that more than four occur, and similarly in 

 the northern ten-armed specimens from Discovery Bay. Such a divergence is very 

 remarkable. The number of spinelets in the transverse comb is also greater (8-10) 

 than generally obtains in C. papposus of similar size. 



Balancing the whole evidence, however, it would appear very doubtful whether the 

 divergence is greater than might be expected in a locational or deep-sea variety, and 

 which we should greatly question the propriety of separating as an independent 

 species from Crossaster papposus. The specimens were dredged in lat. 64 35' N.,long. 

 10 20' W., 290 fathoms. 



* Nyt Mag. f. Naturvidensk. 1877, Bd. xxiii. 3, p. 45. 



