12 ON THE ECHINODERMATA OF THE 



Variations. The preceding remarks respecting the resemblances that occur in 

 the premature phases of three allied species (two of which at least are associated in 

 the same waters) are of themselves sufficient to suggest the existence of ancestral 

 affinities ; and, indeed, so near is the relationship in one case that, although the im- 

 practicability of uniting the whole group is clearly apparent, the propriety of merging 

 two of them, Ps. Falricii and Ps. squamatus, is, in our opinion, far from questionable ; 

 for that Ps. Fabricii is in reality the outcome of locational variation from the 

 squamatus type there would seem to be but little doubt. At the same time it is 

 interesting to note the wide area over which the forms are found distributed and their 

 divergence maintained both Ps. phantapus (teste Sars) and Ps. Fabricii (teste Ayres) 

 being found on the E. coast of North America, and having associated with them two 

 allied forms, viz. Ps. l&vigatus, Ayr., and Ps. granulatus, Ayr., both of which may, 

 without much difficulty, be regarded as derivative forms when the whole group is 

 passed in review. 



Distribution. 



a. Greenland : Holsteinborg, lat. 66 56' N. (' Valorous ' Exped.) ; Jakobshavn, 

 Julianshaab (Lutkeri). 



b. North of American Continent : Newfoundland (Lutken) ; Grand Manan, 2-8 

 fms., adhering to rocks ( Verrill) ; Massachusetts Bay. 



c. ? North of European Continent : Lat. 74 48' N., long. 69 26' E. (Weyprecht & 

 Payer's Exped.), the most northern locality on record. 



Description of the Illustrations of this Species on Plate I. 



Fig. 9. Dorsal aspect of the animal : natural size. 



10. Ventral aspect of the same specimen: natural size. 



11. Ventral aspect of a young specimen : natural size. 



12. One of the small cup-like spicules of the ventral integument: magnified. 



13. Spicules of the ventral integument : magnified. 



CHIRODOTA L^VIS (Fabricius), Grube, Plate I, Figs. 14-19. 



1780. Holoihuria Icevis, Fabricius, Fauna Grcenlandica, p. 353. no. 345. 



1806. ? Holoihuria pellucida (Vahl), Ratbke, Zool. Dan. vol. iv. p. 17, tab. cxxxv. fig. 1. 



1829. Chirodota discolor, Eschscholtz, Zool. Atlas, Heft ii. p. 13, tab. x. fig. 2. 



1833. Pentacta Icevis, Jager, De Holothuriis, p. 13. 



1833. Pentacta pellucida, id. ibid. 



1834. Cucumaria Icevis, Blainville, Manuel d'Actinologie, p. 195. 



1834. Cucumaria pellucida, id. ibid. 



1835. Dactylota Icevis, Brandt, Prodr. Descrip. anim. ab Hertensio obs., fasc. i. p. 45. 

 1835. Dactylota pellucida, id. ibid. 



1835. Chirodota discolor, Brandt, loc. cit. p. 59. 



1837. Pentacta Icevis, Lamarck, Anim. e. Vert. ed. 3, vol. i. p. 553. 



1837. Pentacta pellucida, id. ibid. 



1851. ? Thyonidium pellucidum, Sars, Reise i Lofoten og Finmarken, p. 44. 



1851. ? Synapta coreacea, Agassiz, Proc. Amer. Acad. vol. ii. p. 269. 



1851. ? Synapta rotifera, Pourtales, Proc. Amer. Assoc. Adv. Sci. 1851, p. 15. 



