of North American HeUcidce. 117 



angle." There is, however, a callus at the lower termination of 

 the pillar-tooth, extending nearly 1 mill, in the direction of the 

 upper angle of the lip, which is shown in the figure of the aper- 

 ture, Terr. Moll. III., pi. XL. In Mr. Currier's specimen this 

 callus extends for a short distance across the parietal wall, at a 

 right angle with the tooth, and is thence continued upwards 

 towards, but not so far as the upper angle of the lip. 



I subjoin measurements — 



Diam. maj. 10, min. 9, Alt. 5^ mill. Dr. Gould's specimen. 

 '• " 12 " lOi " 6 " A. O. Currier's " 



It is curious to notice how much the increased development 

 of the charactei's of H. vidtuosa gives to that species affinities, 

 not existing in the typical form, with the group to which H. 

 auriculata belongs. 



But I should remark that some of the North American Heli- 

 ces, especially the toothed species, are by intermediate varieties 

 connected in a marked degree. 



Note on the Toothed Helices of North America. 



The frequent occurrence of toothed shells of the Genus Helix 

 on the ISTorth American Continent is very remarkable. 



In "W". G. Binney's " Check List" of the species of " Eastern 

 North America from the boreal regions to the Rio Grande," 

 published by the Smithsonian Institution, 116 are enumerated, 

 of which no less than 61 have one or more teeth in the aperture, 

 or within the whorls. In his list of the species of the " Pacific 

 Coast from the extreme north to Mazatlan," Binney mentions 

 31 species, of which four have teeth, while 8 have them out of 

 31 luimed (exclusive of those embraced in the Pacific Coast 

 list), in his list of Mexican Helices. Species similarly armed 

 are numerous in the West Indies, and not unfrequent in Cen- 

 tral and parts of South America. 



What office in the economy of the living tenants of the shells 

 these processes, showing much uniformity of design, are des- 



