4 Ech. 
ECHINODERUATA. 
borealis^ Sara, probably belong to tbo same genus as the new arctic species. 
According to Koren & Danielssen (10), they are however congeneric with 
Trochostoma thomsoni, g. & sp. nn., 1. c. pp. 229 et seq., pis. i.-iii. (62® 
44' to 67® 24' N. lat., 1® 46' to 9® E. long.), which presents the following 
characters : — Body subcylindrical, truncated anteriorly, produced poste- 
riorly into a short tail-like portion ; skin highly scabrous from solid 
calcareous bodies and perforated plates ; oral disk with fifteen tubular 
prolongations from the body cavity, separated by an equal number of 
furrows, in the dilated extremities of which are placed fifteen rudimen- 
tary tridigitate tentacula ; vent with five papillae ; no feet ; a polian 
vesicle, madreporic tube, &c. ; two free, ramified lungs (in the young 
state these organs are less developed and mere appendices of the intes- 
tinal cavity, having the same contents, &c.). The anatomy is fully 
worked out. 
Tii^EL (24) has established a new family, Myriotrochidce^ for Myrio- 
trochui rinhi, Stp. (which is redescribed, examined anatomically and illus- 
trated) and Trochoderma eleganSj g. & sp. nn. (Nova Zembla and Karian 
Sea, 5-60 fathoms). Body cylindrical, without feet ; sexes separate as in 
Myriotrochus\ without respiratory organs; skin hard and friable, densely 
studded with several layers of large wheels with 10-16 rays and a muri- 
cate circle ; tentacles six-lobed, ten, without spicules ; one polian vesicle ; 
intestine S-shaped, &c. In this genus, and in Myriotrochus^ the existence 
is proved of ten sense.-organs (auditory ? but without otoliths) placed in 
pairs at the origin of the five nerve trunks. 
Of Oligotrochus vitreus and Stichopus natans^ a detailed account is given 
by the late M. Sars (19), pp. 49-65, pi. vii. 
Elpidia glacialis, g. & sp. nn., Thdel (23), type of a new family, Elpi- 
diidm^ taking, though without lungs, an intermediate positiop between 
Apneumona and Pneumatophora. Body bilateral, back convex, belly flat, 
mouth anterior, but ventral, vent posterior, turned somewhat towards 
the same side ; tentacles ten, cylindrical; four pairs of ambulacral feet, 
lateral, near the margin between back and belly ; feet-like dorsal appen- 
dages, 7-13, approximately biserial; skin semipellucid, thin, friable, 
studded, like the tentacles, the ventral and dorsal feet, with branched 
spicules, a few large wheels, and many small ones of a different structure. 
A soft conical appendage may be protruded from the stiff, almost immov- 
able, ventral and dorsal feet ; from the tentacles, two similar digits from 
the extremity, three from the base (Karian Sea, 75® 24' N. lat., 66® 24' E. 
long., 70-230 metres; off Greenland, 1620 metres). 
' Allied abyssal Holothuriidce are alluded to in “ The Atlantic,” i. p. 132, 
ii. p. 348. To this family further belongs Irpa ahyssicola, Kor. & 
Dan., g. & sp. nn., (10) p. 29, pi. iv., differing through the more elongate, 
almost cylindrical shape of the body, the coriaceous lubrical skin, the less 
ventral position of the mouth, the hand-shaped tentacula with numerous 
(15) digitations ; the lateral ambulacral feet in twelve pairs (nine on 
each side, and six posterior, making twenty-four in all) ; dorsal appen- 
dages, four pairs and two intermediate, all placed anteriorly ; skin with 
few spicules and no wheels ; tentacles, feet, &c., studded with spicules 
(63® 22' N. lat., 1® 20' W. long., 1050 fathoms). 
