K. MITSUKUEI : STUDIES ON 



Specimens examined 



De!?cription : — Tentacles 20. Body elongated, almost cylindri- 

 cal (Theel), or the dorsum vaulted and the ventruin flat (Ludwig). 

 Mouth anterior, subventral. x\nns posterior, terminal. Along each 

 of the lateral ambulacra, a series of large pedicels variable in 

 number (left 30, right 29, Theel; 13 — 25 on each side, Litdwig ; 

 25 on each side, Sluitee). Along the median ventral ambula- 

 crum a double row of smaller pedicels (55 Thkel, G — 14 Ludwig, 

 24 Sluitee) -which are more numerous in the posterior half than 

 in the anterior (in Sluitee's specimen 1 8 in the posterior half and 

 in the anterior half). Numerous dorsal processes (100 Theel) 

 form two longitudinal series, one along each side of the back, leav- 

 ing a rather broad naked area between them ; each series contains 

 several processes ranged side by side, though their arrangement 

 in rows is imperceptible. Some of these processes seem, judging 

 from the ambulacral cavities or vesicles, to belong to the lateral 

 ventral ambulacra. The longest attain a length of 15 — 20 mm., 

 but most of them, being minute and almost rudimentary, are only 

 visible as lighter spots. Calcareous deposits are of two kinds : 

 large wheels and small wheel-like plates. Large wheels are 

 very large, 0.24 mm. in diameter, with 11 — 14 spokes; the felly 

 carries between the spokes round lobes, the number of which is 

 the same as that of the spokes. The large nave is perforated by 



