Body about three times as long as shell, semicylindrical, obtuse in front, forming an acute angle behind; foot extending the whole length, somewhat distinct anteriorly, and carinate behind. Mantle shield-like, covering the back anterior to the shell for about one-fourth its length, not reflected over the shell. Eye-peduncles moderate, slender, two short acute tentacles in front of head. Lingual teeth resembling those of Helix in form and arrangement. Shell entirely external, ear-shaped, nearly flat, about one-third as long as the animal, which it does not half cover when retracted. Spire flattened, forming two horizontal volutions, last whorl enormously expanded and slightly arched. Columella distinct, entire, hiding the interior of the convolutions. _Binneya notabilis_ Cooper. State Coll. Species 988. _Specific characters._—Animal dark lead-colored, with black reticulations, and a wide brown stripe along the median line, extending from the mantle to the front of head, about one-fourth of the total length. Shell with a pale brown, smooth and shining epidermis, extending beyond the margin, translucent when young, becoming thickened by an opaque white deposit on the interior when old. First whorl or nucleus ornamented with about thirty delicate parallel revolving ribs, not concealed by the epidermis, and ending abruptly at the commencement of the transverse lines of growth in the body whorl. Length 0.46, breadth 0.34, height 0.12 inch. This genus resembles _Limax_ in its shield-like mantle, but in the more essential characters of the lingual teeth, appears to belong undoubtedly to the _Helicidæ_. It approaches nearest to the subfamily _Vitrininæ_, in having the mantle in front of the shell, approaching nearest to the _Daudebardia_ of Europe; but differs in the form and opacity of the shell, which resembles some of the _Succininæ_, especially _Omalonyx_ of South America, etc. It differs from these very much in the form of the animal, and the shell being wholly external, forming one of those connecting links which make it difficult or impossible to divide the _Helicidæ_ into distinct groups.