THE SYNAPTID.E OF JAPAN. 



founder, has been obscure untili Clark placed it on a firm basis by 

 revision of the original specimens. The discovery of the present species 

 should serve as a further support for the validity of this singular 

 genus. 



Subfamily III. MYRIOTROCHINiB. 



21. Myriotro chus 'nltii SteensLap. 



Myriotrochus rinkii Steenshap, Videnskab. Mc 1 fr. d. naturh. 

 For., 185 1, pp. 55-60; pl. Ill, figs. 7-10. — Östergren, The Holothuii- 

 oidea of Northern Norway, 1902, pp. 14-18. — Clark, The Apodous 

 Holothurians, 1907, pp. 30-31, 128; pl. VIII, figs. 21-22. — Obshima, 

 Albatross Holothurians (m.s.). 



In the North Pacific this species has been reported from the 

 Bering Strait region, Pribilof Islands and Kamchatka. 



In the Science College Museum there is a specimen of Myriotro- 

 clms, which I may refer to the present species though with much 

 hesitation. It hails from 170 hiro ( = ca. 130 fathoms) in Naka-no- 

 Yodomi, Sagami Sea, having been captured by the late Prof. Mitsu- 

 kuri and Aoki (Cat. no. 1855). The specimen lacks the anterior part 

 and measures only 12 mm. by 3 mm. The wheels are absent on 

 ventrum ; they measure 175-240 fi, on an average 214/i, in diameter; 

 number of spokes 14-19, on an average 14.5 ; peripheral teeth 

 number 23-30, on an average 25.6. I have come across only 

 two cases of exceptionally small wheels, measuring 80^ and 150 /x 

 respectively, but such small wheels do not seem to constitute a dis- 

 tinct class by themselves, as they do in M. tninutus Östergren. Ratio 

 of the number of spokes to that of peripheral teeth ranges from 56.7 

 to 74%, with a mean of 6$%. In Kamchatka specimens I have found 

 the ratio to vary from 60 to 100%, with a mean of 79 %. This 

 seems to stand in accord with the result arrived at by Östergren and 

 Clark, that the number of spokes tends to decrease in specimens from 



