TROPICAL PACIFIC HOLOTHURIOIDEA. 127 



of the spokes is somewhat greater than the diameter of the original hub, a swelling 

 appears near the middle of each spoke and as these swellings widen they come 

 in contact and fuse with each other, leaving the circle of small oval holes, which 

 apparently never fill up. The number of these holes thus corresponds to the 

 number of spokes. The three wheels which were sufficiently complete to permit 

 measurement were 240, 300 and 340 n in diameter, with marginal teeth about. 



Station 4647. Eastern Tropical Pacific, 4 33' S., 87° 42' 30" W., 2,005 fma. Bott. temp. 35.5°. Lt. gy. 

 and br. glob. oz. 



One specimen. 



Although the superficial resemblance of this specimen is very close to that 

 of the smaller of the two specimens of M . giganteus, the wheels are so different, 

 it is impossible to consider it simply an aberrant example of the same species. 

 The question of the relationships of bathybius is discussed under giganteus. 



Myriotrochus giganteus,' sp. nov. 

 Plate 4, fig. 4. 



Length 53 mm.; diameter 20 mm.; oral disk 12 mm. across. Form dis- 

 tinctly like Molpadia but for the lack of any caudal appendage. Smaller speci- 

 men, very much contracted and deformed, 35 mm. long, 9 mm. in diameter 

 anteriorly but only 4 mm. at middle and posteriorly, and with oral disk 7 mm. 

 across. Tentacles twelve, with 5-7 short but distinct digits on each side. 

 Color, of smaller specimen gray; of holotype, light brown on a gray foundation, 

 with area around anus and another area just back of and including tentacles 

 on dorsal side, deep purple. Calcareous ring stout, with the radial pieces having 

 rounded posterior, and broad blunt anterior, projections, and the interradial 

 pieces similar except that the anterior projection is pointed. No stone-canal 

 was found. Polian vessel single, small. Genital glands well developed on each 

 side. 



Calcareous particles are wheels alone, no deposits of any kind being found 

 in the tentacles or oral disk. Wheels (Plate 4, fig. 4) fairly numerous but widely 

 scattered; somewhat more numerous dorsally near the two ends of the animal 

 than elsewhere, apparently, but this may be result of greater abrasion near middle 

 of body. Of twenty-seven wheels observed sufficiently perfect to permit count- 

 ing spokes, two had ten, nine had eleven, eight had twelve, seven had thirteen, 

 and one had fourteen spokes, an average of not quite twelve spokes per wheel. 



l yiyavTtio% = like a giant, in reference to the exceptionally large size for a Myriotrochus. 



