210 K. MITSUKÜKI : STUDIES ON 



body (approaching var. henrici in this respect). In the first speci- 

 men no pedicel can be detected on the median ventral ambula- 

 crum. This is probably due not to their actual absence but to the 

 extreme shrinking which the specimen has undergone. In the 

 third specimen, the first of the median pedicels is somewhat in front 

 of the middle ; at first there is considerable space between them, 

 while they become crowded toward the posterior end. On each of 

 the dorsal ambulacra, some 15 or more conical papillao can be 

 counted ; in reality the number is probably much larger. In the 

 first specimen there is much difference in size, some being large 

 and others smaller, the posteriormost series being especially long. 

 In the second specimen, they seem all about equally slender and 

 long. In both specimens the anterior two or three are in a 

 transverse row. In the third specimen, besides the double rows 

 on each side there are one or two rows of small, low papillœ which 

 seem to be given off" from the ventral lateral ambulacra. 



In the general perisome, large wheels and small wheel-like 

 plates are present. In my specimens, both kinds of these de- 

 posits seem to be as numerous in the ventral perisome as in the 

 dorsal. This is different from what was observed by Theel, who 

 says that large wheels are most numerous in the w^alls of the papillae 

 and the dorsal perisome, while only a few of them occur on the 

 ventral surface and in the pedicels and tentacles. In Sluiter's speci- 

 mens also, numerous wheels and wheel-like plates were present in 

 the dorsal perisome, but in the ventral perisome there were only 

 wheel-like plates and not a single wheel. Large wheels are 

 very characteristic (textfig. 38 a, h). The spokes are rather numer- 

 ous, numbering 12 — 15 in my specimens, 13 and 14 being 

 the most common numbers. Moreover, between every two spokes, 

 there is a roundish plate on the under side, which is visible 



