of North American Helicidos. 99 



carina In a measure obsolete behind the aperture, but modi- 

 fying its form. 



The var. found fossil at Jackson, Miss., is well marked, being 

 ribbed above, the ribs passing over the periphery, with, at the 

 base, an additional less prominent rib between each. I have 

 living examples of the same form from Tennessee, Arkansas, 

 and Louisiana. 



Helix niordax ^huttleworth. 



This was described by Shuttleworth in the following terms : 

 {Bern. Mitth., 1852, Biag. n. Moll, No. 2.) 



T. late et perspective umbilicata, clepressa, sublenticularis, carinata, 

 tenuis, luteo-cornea, strigis rufis interruptis fasciatim ornata, costis vali- 

 dis flexuosis remotis utrinque eximie asperata ; anfr. 5|-, plaui ; apertura 

 perobliqua angulatim lunari-ovalis ; perist. simplex, acutinn. 



Diam. maj. 18, min. 16, Alt. 6 mill. 



JSab. — In mont. Carolinse sept, specimina ultra 12 legit Rugel. 



Obs. — H. alternatse valde affinis, sed costis vahdioribus, ad 1 mill, inter 

 se remotis, distincta. H. Cumberlandiana Lea (forsan mere forma mon- 

 struosa), quacum carina congruit, difFert (ex icone) testa tantum tenuiter 

 striata nee costata. 



Shuttleworth observes that H. mordax being costate is dis- 

 tinct from 11. alternately and also from II. Oumherlandiana, 

 described by Lea as tenuiter striata ; the fact is, that both his 

 own and Lea's species are costate, although the costee in the 

 latter are not so sharp and regular, indeed on the last whorl 

 near the aperture are partially obsolete. Shuttleworth states 

 that his shell agrees, as regards the carina, with M. Cumher- 

 landiana. I have not seen an authentic specimen of H. mor- 

 dax, but looking at the description consider that it bears the 

 same relation to H. Cumherlandiana, as H. Carolinensis to H. 

 obstricta, and although with costse like the southern forms of 

 77. alternata already noticed, being carinated to the extent 

 described, it is a variety of 77". Cumberlandiana. 



