204 



AMERICAN JOURNAL 



No laws of climatology will account for all the differences ob- 

 servable in the various forms I include in these two genera. Pale 

 or colorless specimens may be caused by deficient food or moist- 

 ure, and dwarfs or thin shells by cold or absence of lime ; but 

 we find ours, though nearly allied, preserving their characters 

 under the same circumstances where several live in the same lo- 

 cality. The following table gives at one view the several species 

 and varieties, with their chief characteristics, differing from the 

 Synopsis only as more recent examinations require amendments. 

 Explanatory notes follow, giving the reasons for these amend- 

 ments. The Sections were first used by me in the article in 

 Proc. Cal. Acad. Sci. 1866, p. 259, and correspond to the 

 Groups of the Synopsis, 1867, p. 331. 



In all our Ariontas I have examined I find 4 — 6 ribs on the 

 jaw, as in arbustorum (Albers). In Lysinoe mormonum diudi facta 

 I find 8 ! 



LYSINOE. 



§A(=-Gr. XIII). 



Shining, smooth, or with re- 

 volving grooves ; band usually 

 light-margined. 



a. Whorls 7 to 8, colors 

 mostly dark. 



1. L.fidelis, Gray. 



2. L. Dupetithouarsi, Desh. 



3. L. Ayresiana, Newc. 



b. Whorls 5 — 6 J, paler, band 

 often single in No. 7. 



4. L. Traskii, Newc. 



5. L. Mcmondii, Tryon ? 



6. L. rufocincta, Newc. 



7. L. (var. ?) Gabbi, Newc. 



8. L. facta, Newc. 



Whorls 41. 

 L. Remondii, Tryon (type). 



B (-= Gr. XIV). 



Young hirsute and subangled, 

 adult often rounded, grooves 

 faint or none, bands hidden in 

 young, obsolete in No. 9. 



a. Whorls 6 to 6|, dark. 

 9. L. infumata, Gld. 



10. L. sequoicola, Cp. 



11. L. mormonum, Pf. 



12. L. HillebrandiyN ewe. 



b. Whoi'ls 4 to 4|, 2?aZe. 



13. L. Moivellii, Newc. 



14. L. (var. ?) Lohrii, Gabb. 



