THE APODOUS HOLOTHURIANS 105 



Protankyra ABYSSICOLA. 



Plate IV, Figs. 8-11. 



Synapta ahyssicola Theel, 1886a, p. 14. Calcareous particles, pi. i. fig. 11. 

 Protanl-yra ahyssicola Ostergren, 18986. 



Length. — 65 mm. ; diameter about 5. 



Coi.oR. — Dark yellowish (in alcohol), with considerable reddish pigment at 

 base of tentacles on inner side. 



Distribution. — Eeported from tropical mid- Atlantic, 4,2.30 m. (Theel) ; off 

 coast of New Jersey, 2,468 m. (Theel); off coast of Senegal, 3,200 m. (R. 

 Perrier) ; Gulf of Mexico, 2,259 m. (Clark, antea). Probably distributed through- 

 out the deeper parts of the Atlantic Ocean. 



Remarks. — One of the interesting discoveries of the "Challenger" was this 

 abyssal Synaptid, which has since been taken several times. It is little modified 

 by the great depth at which it lives and fjiows no special peculiarities of structure. 

 There are seven polian vessels. Although miliary granules are wanting in the 

 skin, the longitudinal muscles contain the usual oval particles, and there are 

 nearly straight supporting rods in the tentacles. 



Protankyra pacifica. 



Synapta ahyssicola var. pacifica Ludwig, 1894, p. 174. Calcareous particles, pi. xviii, 

 figs. 13-19. 



Length. — 85 mm. ; diameter about 5. 



Color. — Yellowish white or greenish gray. 



Distribution. — Reported only from outside the Gulf of Panama, in 3,000- 

 3,189 m. (Ludwig). 



Remarks. — As the characters mentioned by Ludwig, which distinguished 

 the Pacific from the Atlantic specimens, appear to be constant, there is no rea- 

 son why this should not be regarded as a distinct species. The anchors and 

 plates are really quite distinct in the two species, when compared side by side. 

 The internal anatomy is not peculiar, but there were ten polian vessels in the 

 specimen examined by Ludwig. 



Protankyra tristis. 



Protankyra tristis Koehler and Vaney, 1905, p. 107. Calcareous particles, pi. xv, 

 figs. 17-18. 



Length. — More than 25 mm. 



Color. — Grayish white. 



Distribution. — Off northern Madras, India, 2,358 m. (Koehler and Vaney). 



Remarks. — Although this species seems nearly related to aculeata, the 

 small size of the anchors appears to distinguish it. Unfortunately, however, it 

 is known only from an anterior fragment. 



