ARCTIC SEA TO THE WEST OF GREENLAND. 69 



that the characters which had hitherto been looked upon as of specific value, are not, 

 as that eminent authority seems to infer, even variations such as can be regarded as 

 dependent on distribution, but must be considered simply the phases incidental to age, 

 together with ordinary individual variation. 



Amongst the specimens procured by the naturalists of H.M.SS. ' Alert ' and 

 ' Discovery ' there are many presenting features developed in a manner which might be 

 regarded as " ultraspecific " when compared with the previously recognized modifications 

 of this " form." In the present state of knowledge, however, it seems preferable to 

 comprehend them under 0. spinulosa of Miiller and Troschel, rather than to burden 

 further the nomenclature with novel designations. 



The mouth-shields and the under arm-plates in this species are subject to very 

 considerable changes and variations, both in contour and in their relative proportions of 

 length to breadth. In large and adult specimens the number and arrangement of the 

 mouth-papillae is also irregular, and not only is there a frequent increase in number in 

 the ordinal horizontal series, but there is also a great tendency towards reduplication of 

 certain papillae in the vertical axis of the Ophiuran. This seems to arise from the 

 longitudinal cleavage of preexisting papillae. 



In young individuals the spinelets of the disk are proportionally long, five or six 

 times their own diameter, and present all the appearances of ordinary embryonic spines. 

 During the progress of growth, however, increase is made in thickness only ; so that 

 when maturity is attained, and the spinelets, along with the disk, are invested with the 

 semitransparent leathery membrane of the body, the appearance is more that of short 

 stumpy prominences than of actual spines a deception which at first sight gives a totally 

 different character to the Ophiuran. 



Coll. Feilden : Discovery Bay, 25 fms., hard bottom ; Cape Frazer, 80 fins. ; 

 Franklin-Pierce Bay, 15 fms., temperature 29 0> 5 Fahr. Coll. Hart: Franklin-Pierce 

 Bay, 13-15 fms., bottom stony. 



Description of the Illustrations of this Species on Plate IV. 



Fig. 11. The upper surface : natural size. 



12. Part of the under surface : magnified. 



13. The spines on the disk: magnified. 



ASTROPHYTID^E. 



* 



ASTROPHYTON AoASSizn, Stimpson. Plate V, Figs. 1-6 a. 



1819. Gorgonocephalw arcticus, Leach, Ross's Voyage of Discovery in H.M.SS. ' Isabella ' and 'Alexander, 



vol. ii. Append. No. iv. p. 178. 



1841. Euryale scutatum, Gould (non Blainville), Invert, of Massachusetts, p. 345. 

 1853. Astrophyton Agassizii, Stimpson, Syn. Mar. Invert. Grand Manan, p. 12. 



1865. Astrophyton Ayassizii, Lyman, 111. Cat. Mus. Comp. Zool. Harvard, i. p. 186. 



1866. Astrophyton Agassizii, Verrill, Proceed. Boston Soc. Nat. Hist. vol. x. p. 344. 

 1866. Astrophyton Agassizii, Ljungman, Ofvers. K.. Vet.-Akad. Fordhandl. 1866, p. 335. 

 1869. Astrophyton Agassizii, Liitkcn, Yidensk. Selsk. Skr. Usekke 5, Bd. 8, ii. p. 66. 



