North American Helicidce. 281 



regarding them. This is particularly the case as to some of 

 the species described by Thomas Say. To a considerable 

 extent it may be attributed to the inaccessibility of Say's wri- 

 tings, now happily remedied by the recent publication of all 

 relating to the terrestrial species by Mr. W. G. Binney. 



Some of the species have been moreover hitherto rare, and 

 seeing how much they vary, an extensive suite of specimens 

 can alone enable a Conchologist to arrive at any satisfactory 

 conclusion on points in dispute. 



The valuable work of the late Dr. Amos Binney, only recent- 

 ly completed under the supervision of Dr. A. A. Gould, has 

 added very much to our knowledge of the subject, but the text, 

 written some years since, scarcely gives the information or the 

 opinions as to several of the groups, which more recent study 

 of them, and the present appreciation of the value of specific 

 characters, would seem to demand and justify. 



It is to be regretted that some of the specimens of the Land 

 shells, deposited by Say at the Academy in Philadelphia, have 

 been lost, and I fear that not all of those remaining are, strictly 

 speaking, entirely reliable. 



Mr. Isaac Lea has described a considerable number of species, 

 and published figures of some of them, but the descriptions are 

 generally by no means ample, and the figures not always satis- 

 factory. 



In Europe there has certainly been disregard of the~writings 

 of American authors, which, with the adoption there of Rafines- 

 quean names, has added to the prevailing confusion. 



Dr. Pfeiffer has published some grievous errors in his works, 

 but has unquestionably been puzzled by the conflicting views 

 of American Conchologists. 



In reviewing the North American Land Shells, we must not 

 overlook the fact, that in no part of the world have species such 

 a wide distribution in latitude, owing it may be argued to the 

 direction, from north to south, of the Rocky and Apalachian 

 Mountain chains. 



