450 ARIONID^. 



internal, and the body attached to the foot in its wliolc lengili. 

 This and the cliaracteristics of the mncus-pore have suggested tlio 

 two sub-families, Arionince and ZonUincc. 



Ocmis AKIOIV, Ferussac. 1819. 



Posterior termination of l)ody obtuse. Integuments crowded 

 with elongated tuberosities on the back, and on the sides with 

 elongated tubercular plates having furrows between. Mantle an- 

 terior, oval, small, covered with granulations, free at the front and 

 on the sides, attached posteriorly, containing in its posterior part 

 numerous fine, calcareous sandy grains. Locomotive disk not ex- 

 panded at the margin, when the animal is fully extended very nar- 

 row, having in some species a narrow median band, and in others 

 not. Respiratory orifice at the anterior margin of the mantle, 

 small. Anal orifice contiguous to the former. Orifice of organs 

 of generation under the two last. On the upper part of the poste- 

 rior extremity of the body is a triangular pore or sinus, with the 

 point directed forwards, a process or projection of the integument 

 serving as a cover to the sinus. 



Jaw with anterior ribs and marginal dcnticulations, broad, 

 crowded. 



The lingual ribbon is broad, composed of a median row of tricus- 

 pid denticles, the central toothlet of each being long and acutely 

 pointed, the side toothlets short and blunt. The lateral teeth are 

 modifications of the central, thirty-one in number, but bicuspid, the 

 inside toothlet of the central being omitted in the laterals on the 

 side nearest the central line, and the teeth gradually changing as 

 they pass off laterally. 



The genus Arion was separated from Limax by M. Ferussac, to 

 contain those species of the latter genus having a terminal pore or 

 sinus. It is universally recognized and has been fortunate in es- 

 caping any confusion of synonymy. 



The internal calcareous grains which represent the shell are in 

 some species isolated, in others aggregated into a nearer resem- 

 blance to the internal plate of Limax. On this distinction arc based 

 the sub-genera Lochea and Prolepis. 



