638 PROCEEDINGS OF THE ACADEMY OF [Dec. , 



agrees with C. Hilgendorfi v. Mart, in everything except 

 the sutural plica which is said to characterize that species. 



2. C. Hilgendorfi v. Mart. Probably a subspecies of C. japonica. 



3. C. oostoma v. Moll. I have considered my C. japonica var. 



surugce to be this species. The latter has a synonym, C. 

 eurystoma subsp. brachyptychia Mlldff. 



4. C. subjaponica Pils. 



The group of C. brevior consists of smaller species, of which the 

 first two, from the middle part of Nippon, have no lunella, while 

 in C. Stearnsii, Addisoni, Jacobiana and hondana a lunella is 

 developed, at least in some individuals. 



5. C. brevior v. Mart. Includes C. tetmptyx Mlldff. 



6. C. nikkoensis Mlldff. 



7. C. hondana Pils. 



8. C. Stearnsii Pils. 



9. C. Jacobiana Pils. 



10. C. Addisoni Pils. 



11. C. stereoma Pils. with varieties nugax and cognata. 



I have elsewhere described and figured C hondana and (7. 

 Stearnsii. C. nikkoensis I have not yet seen. The other species of 

 the brevior group are described below. 



In the typical Stereophcedusce there are either several palatal 

 plicae, or only the upper and lower. In C. hondana, Addisoni, 

 Stearnsii, Jacobiana and stereoma a low, straight lunella stands 

 between the upper and lower plicse. This lunella, in fully adult 

 individuals, is a smooth ridge, without higher points or irregulari- 

 ties; but in some individuals, viewed from the outside, a row of 

 short light markings is seen, as though a series of palatal plicae 

 stood in place of the lunella. When this is not obvious from the 

 outside, it appears when the shell-wall and lunella are viewed by 

 transmitted light. This indicates local differences in the substance 

 of the shell, affecting its refracting qualities; and it occurred to 

 me that a row of plicae is first formed, and subsequently the spaces 

 between them are filled in. Upon examining specimens of C. 

 Jacobiana not quite mature, in which the peristome was not fully 

 formed, I found that this was what actually takes place. Such 

 shells have no lunella whatever, but in its place a series of four or 

 five short plica) (PJ. XXXIX, fig. 68). 



These facts indicate that the ancestral Stereophcedusce had a 



