THE APODOUS HOLOTHUBIANS 101 



sufficient to affect their identify; nor can the slight differences mentioned by 

 Koehler and Vaney ( : 05) as distinguishing timida, and by Fisher ( : 07) as dis- 

 tinguishing albatrossi, warrant our regarding those as distinct species. The 

 anchors are from 240-350 p in length and their plates from 180-270 /. There 

 are two polian vessels and the usual single stone-canal, and in Fisher's ( : 07) 

 specimens there were sense-cups on the tentacles. 



PBOTANKYBA BICOBNIS. 

 ProtanJcyra Hcornis Sluiter, 1901, p. 131. Calcareous particles, pi. x, fig. 15. 



LENGTH. 115 mm., with diameter about 5. 



COLOB. Unrecorded. 



DISTRIBUTION. Reported from near Timor, 828 m. (Sluiter). 



REMABKS. This is a very notable species, unique not only in the remark- 

 able perforated plates, but in the presence of only a single digit on each side 

 of the tentacle, and of four or five stone-canals, while there is only one polian 

 vessel. The anchors are comparatively infrequent, about 330 p. long, and 

 their plates are only 245 /t long and about half as broad. The accessory 

 plates are much more numerous and are sometimes 350 /* in diameter; their 

 perforations are circular and entire. On the whole, bicornis is one of the most 

 interesting holothurians discovered by the "Siboga." 



PBOTANKYRA DUODACTYLA. 



PLATE IV, FIGS. 1-7. 

 ProtanJcyra duodactyla Clark (antea, page 26). 



LENGTH. 60 mm., with diameter about 8. 



COLOES. Clear deep gray. 



DISTRIBUTION. Reported from off the coast of Washington in 1,000 m., and 

 from near Unalaska, Aleutian Islands, in 1,777 m. (Clark). 



REMABKS. This species is related to the preceding in the presence of only 

 a single pair of digits on each tentacle, but there are no accessory calcareous 

 bodies ; there are, however, irregular branched and perforated rods in the ten- 

 tacles. The anchors are 300-360 /* and the plates about 320 /* in length, but 

 few of the latter are complete and only rarely is the bow present. There are 

 two polian vessels and a single stone-canal. 



PBOTANKYBA SLUITEBI. 

 PLATE V, FIG. 27. 



Protankyra sibogce Sluiter, 1901, p. 132. Calcareous particles, pi. x, fig. 16. 

 Protankyra sluiteri Fisher, 1907, p. 729. 



LENGTH.- More than 110 mm. 



COLOB. Unrecorded, but the skin is "thin" and "transparent." 



