EASTERN PROVINCE INTERIOR REGION SPECIES. 203 



erally reacbing to or beyond tlie lower margin of the base of attachment, 

 and always bearing- a distinct cutting point, which last, like the cusp, 

 is usually slender, and projects over the tooth of the adjoining trans- 

 verse line. The side cusps of the reflected portion of the tooth are 

 usually subobsolete, but they are distinctly developed in Z. lasmoclon, 

 sup2)ressus, GundlacM, placentula, gularis, arhoreus, cellarius, Iccvigatns^ 

 signtjicans^ferreus, viridulus, nitidus,fuh^vs, milium. On the side cusps 

 are distinctly developed cutting points in all the species I have ex- 

 amined, excepting Iwvigatus and cellarlns, in which I find no trace of 

 cutting points. These points when present vary in development in the 

 vaiious species, generally disposed to be triangular and somewhat acu- 

 leate in form, thus bearing a resemblance to the cutting point of the 

 marginal teeth. The greatest development of the cutting points is 

 seen in Z. capnodes (Terr, Moll., V, Plate II, Fig. K). The general outline 

 of the central tooth is graceful and slender as compared with the other 

 genera, except Limax and Vitrina. In most of my figures of the teeth 

 of this as well as the other genera I have given only the size of the 

 catting point at its lowest plane, i. e., nearest to the base of attach- 

 ment. It will be understood that from hence the cutting point bulges 

 outward as it rises upwards, and again becomes smaller as it arches 

 above. At its widest development its outline is prominent under the 

 microscope, as in the shaded portion of the cutting point in Plate II, 

 Fig. H, the dotted line showing at the same time the outline at its 

 lowest plane. The lateral teeth in Zonites are of th(5 same type as the 

 central, but are rendered asymmetrical (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 only in 

 Z. Gundlachi (Plate II, Fig. D) that I have observed the inner side cut- 

 ting point, and in this species, even, the lateral teeth are still suffi- 

 ciently asymmetrical to be readily distinguished from the centrals. In 

 Z. Binnei/anus there is also a kind of inner cutting point. As mentioned 

 above, the number of these lateral teeth varies in the respective species, 

 and is so nearly constant as to be, I believe, a good specific character. 

 I find, however, some difficulty in deciding in all cases where the true 

 laterals end and the transition teeth commence, so gradual is the 

 change in some species. Of two Unguals of Z. intertextus examined, I 

 found one to have 12, the other 14, perfect laterals. The number of 

 lateral teeth in the different species is given below. 

 The teeth forming the gradual change from laterals to marginals are 



