ARCTIC SEA TO THE WEST OF GREENLAND. 3 



The tentacles are ten in number, frondose, equal-sized, and very robust in habit. 

 The oral armature is, as a whole, large, although the calcareous mouth-ring in some 

 examples is but very imperfectly calcified. The radial elements are somewhat of 

 the form of an inverted Y, the muscular bands being attached to the extremity of the 

 upward odd prolongation ; the interradial pieces are smaller, and often in the form of 

 a simple arch. The present writers have been unable to detect in any specimens they 

 have examined the secondary ring mentioned by Selenka * ; but in a single small 

 example there seem to be traces of an incipient calcareous prolongation proceeding 

 from the interradial piece, and giving it the " Y " shape similar to that of the radial 

 elements. Perhaps such a development may be a stage towards the structure described 

 by our learned contemporary. 



In a young individual the Polian vesicle is single, and consists of a simple elongated 

 sac, of moderate capacity, and about one third the length of the body. The respiratory 

 organs, the intestine, and the generative organs are largely developed. 



The muscular system is very powerful, the longitudinal bands being of such a 

 breadth as to partially overlay the ampulla? of the sucker-feet ; at the oral extremity 

 they taper off rapidly, and their continuation forms the double band of the extensor 

 muscles of the mouth-apparatus. The TO. retractores are very strong and stout, the 

 band being attached to the mouth-ring between the two fascicules of the extensor 

 muscle. The series of transverse muscles are numerous and closely placed. 



Very conflicting statements occur respecting the calcareous spicules in the cuticle, 

 not only as to the form, but even as to the presence at all of such bodies in C.frondosa. 

 Diiben and Koren described the integument as covered with calcareous granules which 

 are irregular, deformed, and never perforated. Selenka states that he has found no 

 plates whatever in the general body-skin, but only very minute arragonite needles 

 006 millim. in length ; whilst both Semper and Liitken specify that large and 

 perforated plates occur in this Holothuroid, but are only to be met with in the neigh- 

 bourhood of the feet. Our observations tend to confirm the latter naturalists, although 

 there would appear to be very considerable variation in the quantity of spicules present 

 in different specimens. In some examples, for instance, the skin seems entirely devoid 

 of any calcareous deposits whatever, whilst in others spicules are more or less numerous 

 throughout the body ; and this has been the case in moderately large examples. Gene- 

 rally, however, it must be said that spicules are most frequent in the neighbourhood 

 of the ambulacral rows ; but it would seem that no fixed rule of any kind can be 

 definitely laid down as to their occurrence in this species, whilst the same remark would 

 even hold good as to their form. 



Size. This species attains perhaps the largest size of any of the Cucumarice, 

 occasionally measuring a foot from end to end, large specimens being able to extend 

 themselves to twice or three times this length. 



Colour. In colour C. frondosa is of a dark purple mingled with grey, shading off 

 to ashy grey or white on the underside. Young examples are lighter and also of a 

 more uniform shade, generally pinkish or flesh-coloured. 



* " Beitriige zur Anatomie und Systematik der Holothuricn," Zeitsch. f, wiss. Zool. Bd. xvii. p. 347. 



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