220 PROCEEDINGS OF THE ACADEMY OF [1898. 



Our observations may be grouped under four captions : I, Notes 

 on the comparative anatomy of Ariouidce ; 3 II, Classification ; III, 

 Descriptions of the genera and species, and IV, Brief directions for 

 collecting and preparing slugs. 



I. Anatomy of Ariojnid^:. 



General external features. — Slugs of the family Arioniclse vary in 

 external form from the typical Limax shape, to forms with a con- 

 spicuous dorsal hump. The mantle is generally oval, situated anter- 

 iorly on the body, and completely closed over the shell, but in the 

 humped forms it is more posterior and larger, extending some dis- 

 tance in front of the shell, which is more or less exposed. The 

 breathing pore is in its right side near the edge, connected therewith 

 by a gutter. The mantle is adnate at the sides and behind, but 

 free for some distance in front. The foot always has longitudinal 

 " pedal furrows " above its lateral edges, defining a vertically grooved 

 band or " foot margin." The pedal furrows meet at the tail, at 

 which point there is often a " caudal gland," pit or slit developed. 

 The surface sculpture of the integument of the foot is varied in the 

 several genera and species. In Ariolimax there are close parallel 

 grooves above, becoming oblique and more spaced at the sides, and 

 with less conspicuous grooves at right angles to these, uniting them. 

 In Hemphillia, Binneya and A nadenus there is a dorsal groove run- 

 ning back from the mantle, with oblique grooves branching from it 

 on each side. In Prophysaon the surface is divided into a reticula- 

 tion of long diamond shaped meshes by pigmented grooves, each 

 mesh being further subdivided. One species, P. cceruleum, is an 

 exception, having longitudinal grooves as in Ariolimax or Arion. 



The sole is distinctly divided into three longitudinal tracts separ- 

 ated by grooves in Anadenulus. In some other genera (Ariolima- 

 cince) there is an indistinct tripartite division, while in others (Pro- 

 physaon, Hemphillia, etc.), this is not recognizable. 



Shell. — The shell varies in form from a moderately well developed 

 spiral (Binneya) or a convex plate (Hemphillia) exposed entirely 

 or in part by an orifice in the mantle, to a nearly flat, wholly inter- 

 nal plate as in most of the other genera. In some forms of Prophy- 



3 The elementary character of a portion of this paper scarcely calls for apol- 

 ogy in view of the fact that the study of slugs in America is still in an em- 

 bryonic condition. While in Europe there are many expert observers, we 

 have probably not more than four or five men in America who have given 

 especial attention to them. 



