XIX. 
CHARACTERISTIÓ DEEP-SEA TYPES.— ECHINODERMS. 
HOLOTHURIANS. 
Tue order of Apoda among holothurians has neither pedicels 
nor suckers, while the Pedata have a highly developed ambula- 
eral system and a well-defined dorsal and ventral surface, with 
pedicels scattered over the whole body. The large lobes of the 
Elasipoda (the new order of deep-sea holothurians established by 
Dr. Théel) are perhaps tactile. The ventral surface of the Ela- 
sipoda is intended for locomotion, and, as suggested by Dr. 
Théel, they probably move along the bottom with the actinos- 
tome wide open, constantly filling their alimentary canal with 
the ooze stirred up by the tentacles of the mouth. The cal- 
careous deposits resemble those of the larval holothurians, and 
they possess other features showing them to be an embryonic 
type. The auditory capsules are often present in great num- 
bers. 
The Elasipoda are strictly abyssal types, no member of the 
group having been dredged in less than 50 fathoms, and that 
only in the Arctie Ocean, where, as we know, deep-sea types are 
found in comparatively shallow water. Of the large number of 
* Challenger ” species, only five are found within the 500-fathom 
line, as many more inside the 1,000-fathom line, and the others 
all below that limit. At the localities where the * Blake" was 
fortunate enough to find Elasipoda, they occurred in large num- 
bers, and, judging from the contents of the trawl, they appar- 
ently live in communities including several species, and. prefer 
soft ooze. The experience of the “ Challenger " and of the Fish 
Commission was a similar one. The “ Challenger” obtained on 
one occasion no less than ten species associated together. 
