90 T. I \VA K A WA. 



raised lines were prominent ; in some there were one or sometimes two 

 more lines interposed between the first and the second, and in still 

 others another raised line was added above the first. The angular edge 

 of the body-whorl was very prominent in all Yamagata specimens. 



The largest individual of the lot measured 70 mm. in height and 

 55 mm. in diameter, with an aperture 39 mm. long and '29 mm. broad. 



'!) In the specimens from Shinai Swamp in Prov. Rikuzen, eighteen 

 in all, both typical oxytvopis and var. japonica are represented. Eight 

 are referable to the former and the rest to the latter. In all and even in 

 old specimens the apex is uninjured and the shell perfectly smooth, and 

 vividly green in color. The typical oxytvopis specimens, although of 

 normal configuration in young stages, have somewhat lower raised lines 

 than those of Yamagata. This seems to indicate that Shinai specimens 

 have a greater tendency to change into japonica form. 



8) The specimens from a small swamp near the village of Nagahama 

 on the northern shore of Lake Inawashiro are all var. Sciatevi in both 

 the shape and thickness of the shell, but they still retain the character 

 of typical oxytvopis in so far as the prominent raised lines are present. 

 The embryo-shells have typical oxytvopis shape. 



4) In specimens from a canal near the village Shariki, Prov. 

 Mutsu, the definitive characters of var. Sciatevi are settled, although the 

 embryo-shells are typical oxytropis as ever. 



5) The specimens from Hirobuchi Swamp, Prov. Kikuzen, show 

 abundance of transitional forms, typical oxytropis into var. Sciatevi, 

 while the tendency to change into var. japonica is indicated only in a 

 slight degree. In all cases, embryo-shells have the shape of the typical 

 species. 



6) Finally, the specimens collected at Kogawara Swamp, Prov. 

 Rikuchu, are of great interest in that they serve for definitely settling 

 the question as to the mutual relationship of the three forms. The 

 young have invariably the shape and characters of typical oxytvopis 

 (figs. 8 — 11). Among the adults the Sciatevi form prevails. There are 

 besides unmistakable japonica form and others that combine the charac- 



