no. 2073. HOLOTHURIANS FROM NORTHWEST PACIFIC— OHSHIMA. 261 



obliquely overlapping the neighboring one. Their greater diameters 

 range from 20 to 660/*; holes 4 to over 60 in number. Deposits in 

 the introvert are scattered, knobbed plates usually oblong in outline, 

 destitute of spines. These range 95-220// in diameter, holes varying 

 in number from one to above 10. Anal teeth 5, well developed. 

 Pedicels are supported with rather delicate, smooth plates and an 

 end-plate, well developed in ventral pedicels but quite rudimentary 

 in those of dorsum. Supporting bodies of tentacles are either rod- 

 like or plate-like, knobbed or smooth. Calcareous ring tolerably well 

 developed, without posterior prolongations. Retractors inserted to 

 body-wall a little anterior to the middle of body. Polian vesicle and 

 stone-canal single. Respiratory trees two, measuring at most 5 mm. 

 in length, with a few branches. Genital tubes unbranched, in 2 tufts 

 of a few tubes each. Ovarian ova measure about 0.8 mm. in diameter. 

 Genital papilla is found between the middorsal pair of tentacles. 



In female specimens a pair of brood pouches are found on the 

 ventral side, a little anterior to the middle of body. The pouch 

 even when filled with young is not spacious, measuring at most only 

 4.5 mm. in diameter. The wall of the pouch is very thin and con- 

 tains no deposits. In a specimen 16 mm. long, there were 14 young 

 in the right pouch, all polyhedral in shape from mutual pressure. 

 The 29 young contained in the same bottle were probably born after 

 the capture of their mother, and are in the same stage of development 

 as those contained in the pouch but are quite plump and oval in 

 shape. 



The lengths of the young range 1.8-3.2 mm. Body wall is very 

 thick, of a cream color and opaque. Tentacles 10, slightly branched 

 at end, mid ventral pair smaller than the others. Mouth is not yet 

 open, a massive wall forming a low prominence over it. Pedicels 

 present only in trivium, numbering 5-7 in each ambulacrum. In 

 perisome are scattered X-shaped plates with dichotomously branched 

 arms, like those known to occur in the young of O. parva Ludwig. 1 

 In pedicels are found X-shaped deposits similar to, but markedly 

 smaller than, those of body surface. End plate single, sometimes 

 with several holes. Calcareous ring in the form of a network; re- 

 tractors and longitudinal muscles well developed. Polian vesicle 

 single, stone-canal attached to the body wall but not opening exter- 

 nally (?). Alimentary canal coiled, with thick muscular wall. 

 Yolk granules are abundantly found in body wall, body cavity, 

 alimentary canal, and water- vascular system. 



The present species is very closely allied to the antarctic O. laevigata 

 (Verrill), while the peculiarities observed in the young agree very 

 well with those known for C. glacialis as reported by Mortensen, who, 

 however, found three stages contained in a single pouch. The 



1 See Ludwig, Hamburger Magalhamsische Samiuelreise, 1898, pi. 1, fig. 10. 



