164 



ECHINOIDEA. I. 



also really bihainate spiciiles are found, although only in small mimbers. The sphæridiæ (PI. XX. 

 Figs. 13, 18) qnite smooth or a little thorny, sometimes also a little grooved. 



By the Ingolf -Expedition it has been taken on the following stations: 



St 



It is very widely distributed being found in all the arctic seas, and passing far to the south, 

 both in the Atlantic (to the English Channel and Massachnsetts Bay) and in the Pacific (to Vancouver 

 Island and Korea). It is a littoral form, but goes rather deep; by the « Ingolf > it has been taken on 

 a depth of 420 fathoms, and Verrill even mentions it from 640 fathoms (426. p. 540.) 



It is no wonder that a so widely distributed species is very varying; a whole series of species 

 has also been established on more or less marked forms of it. I completely agree with Agassiz, 

 Bell, a. o. that it is qnite impossible to keep the forms described under the nanie oi /^a/lidiis^ graua- 

 laris^ pictns^ and c(iniosiis^) distinct from the typical drohacliioisis or from each other. Forms are 

 not rarely found, to be sure, which mav easily be referred to these forms, but most frequently such a 

 referring will be impossible. I have examined several hundreds of sjDecimens and found all possible 

 transitional forms. Marked local forms seeni not to be found; but as a general thing it may be said 

 that in the Danish seas a more long-spined form is the most common one, at the Faroe Islands a 

 form with numerous short, strong spines and almost without .spicules in the globiferous pedicellariæ 

 seenis to be predominant (most nearly the form grmmlaris); the Icelandic and East-Greenland speci- 

 mens seem upon the whole to have very numerous spicules in the globiferous pedicellariæ, and the 

 Pacific specimens may often be referred to the form car?iosiis\ quite typical drobacliioisis are, however, 

 found so far down as Korea (after .specimens in the museum of Copenhagen). These forms may 

 so far be kept up as distinct varieties, but I do not see that we gain anything by it. Most .specimens 

 it will certaiuly l^e impossible to refer to any decided one of these varieties, and the separate varieties 

 may often be found together. Neither can any difference be pointed out between the forms from 

 shallow water and those from deep water. 



Also the colour is very varying; most common is a grayish white or a somewhat greenish colour, 



With regard to Str. ck/orocen/ro/tis see above p. 120. 



