ARION. 273 



Subfamily ARIOXIN.E. 



Body elongate, attached its whole length to the upper 

 surface of the foot. Mantle shield-like, simple, entirely in- 

 closing a flat, oblong, not spiral shell. Subcaudal gland 

 lunate, transverse, horizontal. 



This subfamily corresponds with the family Arionidae of H. & 

 A. Adams. There are but two genera at present known, Avion 

 aud Geomalacus. The latter has been found only in Ireland. 

 It differs from Arion in having a distinct internal shelly plate, 

 and in the position of the orifice of the reproductive organs 

 being below the right eye-peduncle. 



ARIOX, Fercssac. 



Posterior termination of body obtuse. Integuments crowded 

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

 elongated tubercular plates having furrows between. Mantle 

 anterior, oval, small, covered with granulations, free at the front 

 aud on the sides, attached posteriorly, containing iu its posterior 



Fig. 489. 



Avion ftiscus. 



part numerous fine calcareous sandy grains. Locomotive disk 



not expanded at the margin, when the animal is fully extended 



very narrow, 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 posterior 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. 

 1 8 February. 1869. 



