54 HELICEA. 



Helix thyroides CHEMNITZ, ed. 2, i. 331, pi. Iviii. figs. 8, 9, (1850). 



PFEIFFER, 1. c. iii. 262. 



REEVE, Con. Icon. No. 677. 

 Anchistoma thyroides ADAMS, Gen. pi. Ixxviii. fig. 3. 



I have followed Pfeiffer in the orthography of this spe- 

 cies. Say's manuscript, also, shows the name proposed 

 by him to have been thyroides. 



I have specimens from nineteen States, showing some 

 curious and apparently constant geographical varieties. 

 One from Germantown, Pa., is very small, measuring 

 only 15 millimetres in diameter. It is globose, shining, 

 sometimes imperforate and generally without the parietal 

 tooth. It is impossible to distinguish it from forms of 

 H. bucculenta. Another peculiar form with an elevated, 

 pointed spire and more triangular aperture inhabits St. 

 Simon's Isle, Georgia, (Postell). The species is found in 

 Louisiana and Texas, (Dr. Moore). It also occurs fossil 

 in the Postpleiocene. 



I am unable to find any description of Mesodon leuco- 

 don Rafinesque, quoted in the Boston Journal as a syno- 

 nym. It is probable the name was sent to Ferussac by 

 that author. 



It is also mentioned by Petiver, No. 4, (1. c.) 



HELIX BUCCULENTA GOULD, vol. iii. p. 9, pi. xi a. 



Helix bucculenta PFEIFFER, Mon. Hel. Viv. iii. 271. 

 Helix thyroides $ PFEIFFER, 1. c. i. 345. 



HELIX EXOLETA BINNEY, vol. ii. p. 131, pi. x. 



Helix exoleta DE!YAY, N. Y. Moll. p. 27, pi. ii. fig. 6. 

 Helix albolobris 6 PFEIFFER. Symb. ii. p. 22, absq. desc. 



D. CHEMNITZ, ed. 2, i. 81, pi. x. figs. 19, 20. 

 Helix zaleta MRS. GRAY, Fig. Moll. An. pi. cxci. fig. 9. 



PFEIFEER, Mon. Hel. Viv. i. 316; ii. 270. 



DESHAYES, in Fer. i. 139. 



REEVE, Con. Icon. No. 622, (1852). 



Reeve (1. c.) considers the specific distinction of exoleta 



