HELIX. 77 



Greater diameter, 12 ; lesser, 10 ; height, 5 millimetres. 



Geographical Distribution. Pfeiffer gives Central Ame- 

 rica as the habitat in Chemnitz, but in the Monographia he 

 gives none. The shell figured (fig. 4) is from Tamaulipas, 

 Mexico, where it was collected by Berlandier. I have 

 seen no specimens found strictly within the limits of the 

 Union, though we have every reason to expect to discover 

 them in Texas. 



Remarks. This can be confounded with no known 

 American species. It is at once distinguished by the re- 

 markable aperture, the flat spire, convex base, and umbil- 

 ical channel. It is sufficiently transparent to allow the 

 suture to be seen through the base of the shell, when held 

 towards the light. 



I have given the outlines of the figures in Chemnitz, as 

 well as an enlarged view of the carious aperture. 



The shell referred to doubtfully as a variety of Helix 

 Loisa in my Notes p. 5, may be an immature specimen of 

 Ariadnce. 



Mr. Lea's original specimen of H. Couchiana was ob- 

 tained from the same source as the shell I have figured 

 (fig. 4), and resembles it in every particular. I have not, 

 therefore, the slightest hesitation in placing it in the 

 synonymy of this species. His description is as follows : 



T. superne paulisper elevata, subplanulata, inferne subinflata ; niti- 

 cla, abida, longitudinaliter et subtiliter striata, minute perforata ; anfr. 5 ; 

 apertura rotundata, quinquedentata ; labro subaeuto. 



Hab. Texas L. Berlandier, M. D. 



HELIX HIPPOCREPIS PFEIFFER. 

 PLATE LXXVIII. FIGURE 19. 



Testa anguste umbilicata, depressa, solidula, confertim arcuato-plicata, 

 opaca, fuscula ; spira vix elevata ; anfr. 5j angusti, vix convexiusculi, 

 sutura impressa juncti, ultimus superne carinatus, basi convexior, antice 

 solutus, subito deflexus, pone aperturam constrictus et gibboso-inflatus ; 

 umbilicus extus latiusculus, angustissime pervius ; apertura subhorizon- 



