66 
THE VOYAGE OF H.M.S. CHALLENGEK. 
exteriorly, and measure as much as 0‘15 mm, in length, while the buttons (PL V. fig. 3, 6), 
on the contrary, have a more constantly regular form and a length of about 0‘1 mm. 
Probably, it will at once be stated that the species in question is identical with one 
of the before-mentioned species, these being younger forms, but for the present I think 
it better to hold them apart. 
The small individuals mainly differ from Cucumaria salmini by the want of anal 
teeth, from Cucumaria dubiosa by the fact that the pedicels are present even in the 
ventral interambulacra, and from Cucumaria hoelliheTi by the number of Polian vesicles 
and by the simple genital tubes. Cucumaria dubiosa is possibly a young individual of 
Cucumaria koellikeri. 
Cucumaria abyssorum, n. sp. (PI. IV. fig. 6 ; PI. XVI. fig. 6). 
Body inflated, fusiform, with the posterior extremity tapered, caudiform. Tentacles 
ten, of almost equal size. Anus without teeth. Pedicels completely retractile, thinly 
distributed in a double alternating row along each ambulacrum. The spacious inter- 
ambulacra naked. Integument thin and soft, supported by scattered, rather large 
four-armed calcareous bodies with the ends of the arms dilated, spinous and pierced by 
some holes ; one of these arms especially is more developed, provided with more spines, 
and communicates to the surface of the body a certain degree of roughness. Pedicels 
strengthened by terminal plates and straight or slightly curved rods with the ends dilated, 
perforated and spinous, and with a larger or smaller spinous process in the middle ; 
sometimes this process is larger and perforated. Colour in alcohol, yellowish-white. 
Length, 45 mm. 
Station 147, December 30, 1873 ; lat. 46° 16' S., long, 48° 27' E.; depth, 
1600 fathoms; bottom temperature, 34° ‘2; Diatom ooze; seven specimens. Station 
156, February 26, 1874 ; lat. 62° 26' S., long. 95° 44' E. ; depth, 1975 fathoms; Diatom 
ooze ; three specimens. 
The largest individual is remarkable in possessing only nine tentacles, but this can 
only be an abnormality. A single Polian vesicle and madreporic canal are present. The 
calcareous ring (PI. IV. fig. 6, a) is not very well developed, and has no posterior 
prolongations. The retractors communicate with the muscular bands nearer the anterior 
end than the middle of the body. Anteriorly, the alimentary canal is provided with a 
very powerful, expanded, muscular stomach. The reproductive organs consist of short 
simple tubes arranged in a bundle on each side of the dorsal mesentery. The respiratory- 
trees have comparatively few and short branches, scattered all over their length. 
The perisome is soft and pliable ; its calcareous deposits (PI, IV. fig. 6, b) are more 
thinly scattered. The diameter of the deposits measures 0'3 mm,, and sometimes 
they bear some spines not only at the ends of the arms, but even in their middle. 
