110 THE .NAUTILUS. 



occasional extra development, have been very generally ignored. 2 

 Even "families" have been based on the presence or absence of the 

 caudal pore; but it need hardly be said that such groups are 

 violently unnatural. 



It is now proposed to unite all of the groups having the pedal 

 grooves developed, into a superfamily to be called AULACOPODA, 

 equivalent in value to the AGNATHA (so-called, including Seleni- 

 tidce), or to the group composed of Helieidie, Bulimulidce, Oylindrel- 

 liihe, Pupidce and Achatinid(e, which may be called HOLOPODA. 



The American Atilacopoda may be tabulated as follows: 

 I. Marginal teeth with narrow, lengthened basal-plates, either uni- 

 cuspid and thorn-like, or bicuspid by elevation of outer on 

 middle cusp. 



a. Foot-margin wide; shell more or less spiral; ovotestis 



imbedded in liver, ZOSITIDJE. 



mi. Foot-margin narrow ; shell a flat internal plate, not 



spiral; ovotestis free from liver ; slugs, LIMACIDJE. 



II. Marginal teeth with short, wide and squarish basal-plates with 



one or several casps, the outer cusp never elevated on middle 



cusp. 



a. Shell spiral, usually wholly external, ENIJODONTID.E 

 int. Shell non-spiral, internal, more or less obsolete or want- 

 ing; slugs. 



b. A vestigial shell present . ; mantle small, anterior, 



AKIONID.E. 



lil/. No shell ; mantle covering the whole upper sur- 

 face, PHILOMYCID.K. 

 Most of these families contain genera with, and genera without a 

 caudal mucus pore. The Limacidie and Arionidce are degenerate 

 so far as the shell is concerned, and have doubtless descended from 

 the ancestral Zonitidve and Endodontidee respectively. 



Xortk American Genera. 



ZONITID.T-: comprises Omplialinn, \ r itrinLtmH<v, Vifrc<i,Gtinti-oiliiiiln. 

 Poecilozonites, Guppya, Conulus, Pristiloma and Vitrina. See NAU- 

 TILUS, June, 1895, p. 18. 



2 Exceptions need not be noted here; but 1 cannot refrain from mentioning 

 that the importance of the pedal grooves has been fully recognized by a bril- 

 liant Australian malacologist in dealing with the Charopa group. 



