534 



C. H. EDMONDSON AND R. II. KINGMAN. 



•Qoadr niella Cockerell. Q. symmetrica Schultze ; Q. symmetrica var. 

 curvata Wailes (fig. 7). 



Very typical forms of the species were taken from shallow lakes 

 on Mt. Rokkozan. The variety, observed but once, was found in 

 Lake Hakone. 



Nebela Leidy. N. collaris Leidy ; N. crenulala Penard ; N. hippo- 

 crepis Leidy (figs. 8, 9) ; N. triangolata Lang (figs. 10-14). 



In the material collected in Japan species of Nebela were very 

 rare. 



There can be no reason to believe, however, that the genus is 

 not well represented in that country. One individual of the rare 

 species, N. hippocrepis, was found in material from Mt. Rokkozan. 

 In the ooze from the rocks along the shore of Lake Hakone and 

 from the border of a shallow lake on Mt. Rokkozan was found a 

 species which is here listed under the name N. triangolata Lang. 



The Japan species resembles, in some particulars, Nebela bipes 

 Carter, as described in Clare Island Survey, Part 65, by Wailes 

 and Penard, and may represent an intermediate form between N. 

 triangolata and N. bipes. 



In the Japan form the shell is very transparent, compresed, 

 irregular in outline with the fundus region inflated in an asymmet- 

 rical manner. The aperture is slightly oval. 



Great variation exists in the form of the shell and in the arrange- 

 ment of the plates. In some the plates are circular or oval, 

 distinctly separated from each other with the ground substance of 

 the shell intervening. In others the plates are closely crowded 

 together and very irregular in outline, while in some the plates are 

 regular in outline but distinctly overlap each other. 



The irregular inflation of the fundus is a characteristic feature. 

 Usually the posterior lateral borders are expanded into lobes of 

 variable size. In some these prolongations are pointed as in N, 

 bipes, but more often they are blunt or rounded. Occasionally the 



