ARCTIC SEA TO THE WEST OF GREENLAND. 13 



1851. Chiridota lewis, Grube, Middendorff's Sibirische Reiso, Bd. ii. p. 41. 



1851. ? Chiridota discolor, Grube, Middendorff's Sibirische Reise, Bd. ii. p. 35. 



1852. Trochinus pallidus, Ayres, Proc. Boston Soc. Nat. Hist. vol. iv. p. 243. 



1853. Chirodota Icevis, Stimpson, Mar. Invert. Grand Manan, p. 17. 



1857. Chiridota lave, Liitken, Vid. Mcddel. N. Forening i Kjobenhavn, 1857, p. 16. 



1861. ? Chirodota pellucida, Sars, Oversigt af Norges Echinodermor, p. 124, pis. 14-16. 



1862. Chirodota Icevis, Dujardin & Hupe, Hist. Nat. Zooph. ISchinodormes, p. 616. 



1866. Chirodota Iceve, Verrill, Proceed. Boston Soc. Nat. Hist. vol. x. p. 354. 



1867. Chirodota pellucida, Selenka, Zoitsch. f. wiss. Zool. Bd. xvii. p. 366. 

 1867. ? Chirodota tiyillum, Selenka, ibid. 



1867. ? Chirodota typica, Selonka, ibid. 



1868. Chirodota Icevis, Semper, Holothurien, Reise im Archip. d. Phil. pp. 23, 267. 



1868. Chirodota pellucida, Semper, Holothurien, Eeise im Archip. d. Phil. pp. 23, 267, pi. v. fig. 2. 



Body elongate and cylindrical, to which the absence of sucker-feet and of all 

 hooklets or asperities imparts a strikingly vermiform appearance. Specimens preserved 

 in spirit, however, are extremely contracted and generally contorted out of all natural 

 shape. The skin is smooth, whitish, and semitransparent in spirit preparations ; and 

 the longitudinal muscles form five dense white bands extending from end to end and 

 prominently marking out the interradial spaces. Within these areas are found a 

 number of milk-white spots or sac-like papillae, ranging up to a millimetre in diameter, 

 and arranged in three of the interradia (which may be regarded as the dorsal area) in a 

 fairly continuous line of about 20 to 30, whilst in the remaining two interradia, which 

 form the ventral surface, there are not more than from 3 to 12, and these confined 

 generally to the extremities, principally the anterior one. The white excrescences or 

 sacculi are not all of uniform size ; for a smaller one frequently alternates with a larger ; 

 and they contain a collection of the elegant wheel-shaped spicules which charac- 

 terize this genus ; and of these there may be as many as 90 or even more in the large 

 spots. The wheels measure O'l millim. in diameter, and are uniformly six-rayed; the 

 edge of the rim is bent over inwards and finely denticulated, a character which is only 

 perceptible under certain methods of illumination ; and this, as well as the manner in 

 which the " spokes " are attached to it, seems to have been frequently misunderstood, 

 and to have given rise in consequence to much diversity of opinion, since the differences 

 were considered to be of specific importance. 



The tentacles are twelve in number, and somewhat hand-shaped ; and the digita- 

 tions, of which there are 10-12, are capable of being closed in upon the " palm." The 

 tentacles contain a few small spicules, which in the " fingers " are little more than 

 simple elongate bodies ; but nearer the base their extremities are enlarged and frequently 

 either cleft or crenulate. 



The mouth-ring is very compact, the elements being in such firm adherence as to 

 convey the idea of a solid annul us ; they are subquadrate in form, having the lower 

 margin incurved, and on the upper a slight prominence with a small hollowing-out of 

 the margin on either side of it ; five of the pieces (alternately placed) are punctured for 

 the nerve. On the unpunctured plates there is an elevation or crest-like prominence, 

 somewhat in the form of an inverted Y. 



