North American Helicidce. 29 



The following are the measurements of the largest and 

 smallest specimens, selected from about thirty of those col- 

 lected by Mr. Dorman : — 



Diam. maj. 16, min. 13, Alt. 1h mill. 

 " " 12, " lOi, " 6 " 



I have no authentic inforraiation of the occurrence of this 

 species in any other locality than at St. Augustine, and its 

 immediate neighbourhood, and no other form was there found 

 by Mr. Dorman. 



It is difficult to understand Say's observation as to the dif- 

 ferent size of the male and female, referring, as he evidently 

 does, to the shell, and not to the anhnal. His measurements 

 correspond with those of the smaller diameters of my speci- 

 mens. 1^0 example with the indistinct bands mentioned by 

 Say has come under my notice. 



Ko fulcrum or tubercle exists in any member of this group. 

 The groove in the last whorl, exhibited in the umbilical region, 

 has a corresponding somewhat convex surface in the interior. 



I would explain that the forms figured as auriculata by 

 Binney in Terr. Moll., pi. xL, fig. 1 (right hand), by Ferussac, 

 pi. 50, fig. S, and by Reeve in Conch. Icon., pi. cxix., Ko. TOO, 

 appear to represent the same species, — one which I consider 

 distinct, and propose to describe as H. auriformis. 



Binney's fig. 2 in both his works, and Eeeve's pi. cxxi., No. 

 720, may be of a different shell, but cannot in fact be very 

 readily made out, — the figs.l, 2 in Chemn., pi. 55, are quite unin- 

 telligible ; certainly none of them are of IL avara Say. To 

 another distinct species from Georgia, confounded with H, 

 avara, I give the specific name Postelliana. 



