40 THE VOYAGE OF H.M.S. CHALLENGER. 



The above specific characteristics chiefly refer to the individuals from Station 50 ; the 

 only specimen obtained from Station 150, which I have had at my disposal, was most 

 incomplete; it differs in some ways from those of the first-mentioned station, and wdl, 

 when compared with individuals in a more complete state, possibly prove to belong to 

 another species differing from this one. The want of necessary materials, and the strong 

 general resemblance it bears to this species, induce me to leave it here provisionally ; 

 but I intend, after having first given a more detailed account of the typical form, 

 to point out by what this one is distinguished. A short time after my Prelimin- 

 ary Eeport on the Holothuridse of H.M.S. Challenger had been communicated to the 

 Royal Swedish Academy of Science, and before it was printed, I received from Drs 

 Danielssen and Koren their report upon the Echinoderms of the Norwegian North 

 Atlantic Expedition, in which a new Holothurian, Kolga hyalina, is described most care- 

 fully ; this species bears a strong resemblance to Kolga nana, described by me, and at 

 first I considered the two forms to be identical. From want of material I have not 

 had the opportunity of making comparisons, and, as several differences exist, I have pre- 

 ferred to keep Kolya nana in the meantime as a separate species. 



All the specimens which have been brought home by the Challenger expedition are 

 more or less injured, the most of them being torn in pieces, consequently they are neither 

 suitable for determining the outer form, nor for rendering an examination of the inner 

 organs possible. The body is elongated, ovate, and reaches its greatest breadth at the 

 middle or a little behind it ; its posterior extremity is evenly rounded, whde the anterior 

 one is almost truncated ; the mouth and tentacles are terminal, indistinctly bent towards 

 the almost flat ventral surface. The dorsal surface is not very strongly convex, 

 the breadth of the body being always greater than the height. The ends of the 

 tentacles are divided by some small incisions round the edge into four or five small pro- 

 cesses or lobes, each carrying some smaller retractfle branches ; in most cases, the 

 terminal part being retracted, only one or two processes are to be seen. The processes 

 of the dorsal surface are small, decreasing in size backwards, so that the last pair is 

 minute ; sometimes four pairs of processes are to be observed instead of three, which 

 seems to be the ordinary number. As they are usually crowded in each row, and webbed 

 together at the base, they appear to project from a low ridge, caused by the contraction 

 of the animal ; some fully extended specimens seem, however, to have the processes at 

 some distance from each other and projecting directly from the body-wall. The pedicels 

 are eight or in most cases nine in number along each side of the ventral surface ; 

 the posterior pairs are always considerably smaller. Among the calcareous deposits 

 of the integument, the extremely arcuated spicula (PI. XXXIV. fig. 5), often almost 

 curved in the form of a ring, are especially numerous, but very small and insignificant, 

 and slightly enlarged in their middle ; they are partly scattered, partly aggregated, 

 and generally provided with spines. The plates, on the contrary, are perforated so as to 



