THE APODOUS HOLOTHUKIANS 129 



Remarks. — Ostergron ( :03) appears to liave clearly established the right of 

 this species to recognition. In addition to the differences between it and the 

 preceding species already mentioned, Ostergren emphasizes the form of the 

 longitudinal muscles, which are broad, flat, and thin in vitreus, even anteriorly, 

 instead of narrow and much compressed anteriorly, as in rivYii; and the 

 tendency of vitreus to autotomy. 



Myrioteochtjs minutus. 

 Myyiolnii-hus minutus Ostergren, 1905&, p. cxciv, fig. I A. 



Length. — 6-10 mm. 



Color. — Practically wanting; body-wall thin and nearly transparent. 



Distribution. — Reported only from the coast of Korea, at a depth of 60-65 

 m. (Ostergren). 



Remarks. — This little synaptid is of special interest because of its having 

 numerous sup])orting rods in the tentacles, in which it is unique in the sub- 

 family; and its having the alimentary canal connected with the body-wall in 

 a manner somewhat different from that of any other holothurian. Its geograph- 

 ical position is also unique, no other member of the subfamily occurring any- 

 where nearly so far south. 



Myriotrochus theeli. 



Myriotrothus theeli Ostergren, 1905a, p. clix. 



Length. — 12-15 mm. 



Color. — White, half transparent. 



Distribution.— Reported only from northwest of Jan Mayen, 72° 42' N. and 

 14° 49' W., at a depth of about 2,000 m. (Ostergren). 



Remarks. — This interesting species is notable for the great depth at which 

 it is found, showing that, like Acanthotrochus, it is a true deep-sea form. Only 

 five specimens have been taken. 



TROCHODERMA The'el, 1877. 



Tentacles 10. Calcareous deposits consist exclusively of wheels with 10-16 

 spokes ; the rim with scattered somewhat pointed knobs, but without teeth pro- 

 jecting horizontally inward. These wheels lie in the skin in so many layers as 

 to make the body-wall quite firm. 



This monotypic genus is easily recognized by the form of the wheels, which 

 are quite different from those of any other synaptid. 



