ARTON. 233 



Jaw and dention as in Avion (PI. 45, figs. 17, 18). 



One species, H. glandulosa. B. and Bl. Oregon. 



Differs at first sight from all the preceding genera in its 



exposed shell. 



** No mucous pore. 



Genus ANADENUS, Heynemann, 1863. 



Limaciform, subcylindrical, tapering behind , mantle large, 

 granular, anterior, concealing a shell-plate; no mucous pore; loco- 

 motive disk distinct ; respiratory orifice median or posterior ; 

 genital orifice behind and below the right eye-peduncle. Shell- 

 plate small, oval, flat, nucleus medio-posterior. 



Jaw costulated ; dentition as in Arion (PL 45, fig. 16). 



A. giganteus, Heynemann. Himalaya Mountains. 



Genus PROPHYSAON, Binney and Bland, 1873. 



Without distinct locomotive disk ; respiratory orifice a little 

 anterior on the right margin of the mantle ; otherwise like 

 Anadenus. Shell-plate subhexagonal. 



P. Hemphilli, Biun. and BL Pacific Region of U. S. 



Dr. Fischer makes this a subgenus of Anadenus. Dentition 

 and jaw (PL 45, figs. 23, 24). 



Genus CRYPTOSTRACON, W. G. Binney, 1879. 



Animal limaciform, subcylindrical, attenuated behind; mantle 

 slightly anterior, thin, small, concealing the shell; no mucous 

 pore ; respiratory orifice on the middle of the right margin of 

 the mantle. Shell internal, sigaretiform, rudimentary, large as 

 the mantle, membranous, subspiral^ with postero-lateral nucleus. 



Jaw and dentition as in Arion (PL 45, figs. 19, 20). 



One species, G. Gabbi, Binne}^ Costa Rica. 



Genus ARION, Fer., 1819. 

 Section LOCHEA, Moquin-Tandon, 1855. 



A. RUFUS, Linn. PL 56, figs. 11-15; PL 57, figs. 16, 17, 22. 



Robust, large, strongly rugose, somewhat rounded at either 

 extremity, not carinated; unicolored or striped, not maculated; 

 shield oval, granular, not gibbose ; pulmonary orifice anterior, 



