of North American IlelicidcB. 101 



sually large specimen, said to be from Tennessee, I am indebted 

 to Mr. Henry Van Nostrand ; it measures, 



Diam. maj. 23, min. 19, Alt. 9 mill. (6 whorls). 



The comparatively smooth Ohio form is, 



Diam. maj. 19, min, 16, Alt. 7 mill. (5^ whorls). 



A small variety from Goat Island, N. Y., is, 



Diam. maj. 13, min. 10^, Alt. 6i mill. (5 whorls). 



A variety found by Mr. H. Van Nostrand, at Delaware 

 AVater Gap, Pa., has very rigid somewhat distant ribs. 



The position of the upper lip-tooth in this species is not abso- 

 lutely constant, its distance from the lower one is variable. 



Helix triodonloides noT. sp. 



Plate IV. fig. 11-12. 

 T. perforata, globoso-depressa, tenui, subpellucida, pallidc cornea, 

 snperne subobsolete costulato-striata, basi convexa, leevigata ; spira 

 brevi ; anfr. 5 convexiusculis, ultimo prope aperturam plicato, antice 

 deflexo ; apertur^ rotundato-lunari, obliqna, coarctata ; perist. reflexo, 

 calloso, marginibus dente linguiformi, acuto, triangulari junctis, dextro 

 dente in margine calli posito, basali dente obliquo munito, ambobus den- 

 tibus parvis, inter se remotis. 



Shell perforate, globose-depressed, thin, subpellucid, pale 

 horn-colored, with partially obsolete rib-like striae above ; base 

 convex, smooth ; spire short ; whorls 5, somewhat convex, the 

 last plicately ribbed near the aperture, deflexed anteriorly ; 

 aperture roundly lunate, oblique, contracted ; perist. reflected, 

 callous, the margins joined by a sharp linguiform triangular 

 tooth, the right with a tooth on the margin of the callus, 

 basal with an oblique tooth, both teeth small and far apart. 



Diam. maj. 91-, min. 8, Alt. 5 mill. 



Habitat. — De AVitt Co., Texas, Dr. ISTewcomb ! ; Corpus 

 Christi, Texas. 



Remarhs. — It has been generally assumed that the H. trio- 



