192 Quarterly Joicrnal of Conchology. 



quadrate marginal teeth. 



The second division is distinguished by the presence of a jaw, 

 and we find in this division also the same grouping of genera into 

 those with quadrangular and those with aculeate marginal teeth. 



The following genera possess teeth of the aculeate type : Lwtax, 

 Ibycus, Parmacdla, Teftientia, Maiiella ?, Parmarion, Dendrolimax, 

 Phosphorax ?, Urocydus ?, Viirina, Vttrinoidea, Vitrinopsis, Nan- 

 ina, Stenopus, Vitrinoconus, Macrocydis and Zonites. The remaining 

 genera have quadrate marginal teeth, and are subdivided into three 

 sections which are divisible by the character of the jaw, which is 

 either in one single piece, one single piece with an accessory upper 

 quadrate piece, or in numerous pieces. 



Those genera belonging to the first subdivision — with the jaw in 

 one single piece — are formed into groups based on the absence, 

 presence and peculiarities of the ribs of their jaw. But these 

 divisions are not perfectly satisfactory', owing to the variability of 

 these characters. 



Of the genera without ribs are — Philomyais, Parmella, Oopelta, 

 Afiaderus, Sagda, Pattila, Polymita, Hemitrochus, Helicodiscus, 

 Acavus, Gorilla, Caryodes, Pajida, Labyyinthus, Caracollus, Leiico- 

 chroa, Cystuopsts, Plagioptydia, Leptoloma, Anostoma, Anostomdla, 

 To/nigerus, Boysia, Pledosto??ia, Hypselostoma, Adiatinella, Clau- 

 silia, Stenogyi-a, Strophia, Bidiminus, Balea, Pupa, Vertigo, 

 Ferussada, Ccedlianella, Geostilbia, Azeca, Tornatella, Zospeum, 

 Holospira, Eiicalodium, Coelocentrum, Lithotis, Rhodea, Megaspira, 

 Limicolaria, but one species has a ribbed jaw, Adiatina, Pseud- 

 adiatina, Perideris, Cohinina, Btdiimts which however as now con- 

 stituted has various forms of jaw. 



The genera of the second subdivision have decided stout ribs on 

 the jaw and are the following: — AiHoii, Ariolimax, Prophysaon, 

 Pallifera, Veronicella, Birmeia, Hevphillia, Helix, Geomalaciis, 

 Letournexia, PeUella, Xanthonyx, Simpnlopsis, Pfeifferia, Berendtia, 

 and some species now included in Bvlivms, Codilostyla, Buli- 

 minus, and Limicolaria. 



The . genera Gceotis, Ainplrili/lima, B^diniulns, Cylindrella 

 Macroceramus, Piueria, Partula, forming the third subdivision, have 



