452 PHILOSOPHY OF ZOOLOGY. 



consists were formerly confounded with those which now 

 constitute the restricted genus Limax. It differs, liowever, 

 in possessing the mucous pore, in the pulmonary orifice be- 

 ing near the anterior margin of the shield, with the sexual 

 orifice underneath, and in the soft state of the calcareous 

 matter, in the shield. The author now quoted, has de- 

 scribed four species, and illustrated their characters by 

 beautiful and expressive figures. The Limax ater (toge- 

 tlier with its variety riifits) of British writers may be re- 

 garded as the type of the genus. 



13. Plectrophorus. — A conical protuberant shell at 

 the termination of the cloak. 



This genus, likewise instituted by M. FerrussaCj nearly 

 resembles the preceding in form. Three species have been 

 described and figured, which, however, differ remarkably 

 from one another. 



2. KxtremUy of the Tail simph. 



The genera of this group have neither a terminal mu- 

 cous orifice nor shell. 



14. Limax. — Pulmonary orifice near the posterior mar- 

 gin of the shield. 



This genus, as now restricted by M. Fj:rrussac, differs 

 from the Arion in the absence of the caudal mucous pore, 

 the jxjsition of the pulmonary cavity, and the orifice of the 

 sexual organs placed under the superior right tentaculum. 

 The calcareous matter of the shield is more solid, and ap- 

 pears as a shelly plate. Six species have been described 

 and figured. The Limax cinereus of Lister is the type 

 of the genus. 



15. LiMACELLus. — Pulmonary orifice near the anterior 

 margin of the shield. 



This genus was instituted by M. de Blainville, in the 

 Journal de Physique^ December 1817, p. 442, pi. 11, f 5, 

 nov. His observations were made on a specimen in a shri- 



