162 PROCEEDINGS OF THE ACADEMY OF 



I give in fig. 5 a general view of tlie arrangement of the teeth 

 in Zonites} The centrals liave a base of attachment longer than 

 wide, subquadrate, with lateral expansions at the corners of the 

 lower margin. The reflected portion varies in size in the various 

 species, from highly developed in viridulus (pi. XVII., fig. 6) and 

 others, to slightly developed in lasmodon (pi. III., fig. 7) and 

 others ; in the latter case resembling the short reflection of Vitrina. 

 The reflection always bears a more or less developed central 

 cusp, generally reaching to or beyond the lower margin of the 

 base of attachment, and always bearing a distinct cutting point, 

 which last, like the cusp, is usuall}^ slender, and projects over the 

 tooth of the adjoining transverse line. The side cusps of the 

 reflected portion of the tooth are usually subobsolete, but they are 

 distinctly developed in Z. lasmodon (pi. III., fig. T), supjyressus (pi. 

 XVII., fig. 11), Giindlachi{\)\. III., fig. \0)^capsella (fig. 4),gularis 

 (fig. 1), a7'boreus (pi. XVII., fig. 4), cellariiis (pi. II., fig. 3), Isevi- 

 gatus {fig. 1, 2),significans (pi. XVII., fig. 10), ferreus (pi. XVII., 

 fig. 9), viridulus (pi. XVII., fig. G), nitidus (pi. XVII., fig. 7), 

 fulvus (pi. XVII., fig. 5), milium (pi. XVII., fig. 8). On the side 

 cusps are distinctl}' developed cutting points in all the species I 

 have examined, excepting Isevigatus and cellarius, in which I find 

 no trace of cutting points. Xhese points when present vary in 

 development in the various species, generall}'^ disposed to be tri- 

 angular and somewhat aculeate in form, thus bearing a i*esem- 

 blance to the cusp of the marginal teeth. The greatest develop- 

 ment of these cutting points is seen in Z. capnodes (pi. II., fig. 6 ; 

 pi. III., fig. 12). I have given on pi. III., fig. 12, an enlarged view 

 of a central in Z. capnodes ; abed gives the base of attachment, 

 e the reflected portion of the tooth, //the subobsolete side cusps, 

 h the median cusp, i the cutting point of the median cusp, g g 

 the cutting points of the side cusps. The general outline of the 

 central tooth is graceful and slender as compared with the other 

 genera, except Limax and Vitrina. 



The lateral teeth in Zonites are of the same type as the central 

 but are rendered unsj'^mmetrical (as usual in the land shells) by, 

 the suppression of the inner, lower, lateral expansion of the base 

 of attachment and the inner side cusp and cutting point. It is 



' The characters of the separate teeth of this species are better shown in 

 pi. XVII., fig. 3. 



