334 MEXICAX BO VXD A li T SHELLS— DA L L. 



Nuevo Leon and Tamaulipas. After the survey of the boundary came 

 the surveys for a route for a Pacific railway, in which a number of the 

 same oflScers were employed. By tliem and by other members of the 

 parties engaged, a few mollusks were collected, including several fossil 

 forms from the Colorado desert. Dr. John L. Le Conte and Prof William 

 P. Blake were among the contributors, and the mollusks were reported 

 on by T. A. Conrad and Dr. A. A. Gould. 



At a later date naturalists settled in California, and either directly 

 or through the aid of collectors, obtained a few species from the bor- 

 ders of this region, which were described by Kewcomb, Cooper, Yates, 

 and others. After the establishment of the State geological survey 

 contributions collected in Sonora were received from August llcmoiid, 

 and from Lower California, collected by W. M. Gabb. Dr. Horn, of 

 the Army, sent some interesting species from Fort Grant, Arizona, 

 to Gabb, which Avere described by the latter. Under the auspices of 

 the Smithsonian Institution collections were made in the vicinity of the 

 boundary, by Dr. Edward Palmer. Later still, parties connected with 

 the Department of Agriculture and the United States GeologicalSur 

 vey worked in the same region and a few species were added to the list 

 of those known through explorations by Dr. A. K. Fisher, Yernon 

 Bailey, Mr. Lloyd, Dr. C. Hart Merriam, E. W. Nelson, and others, most 

 of which were reported on by Dr. R. B. C. Stearns. 



Collections made by the French in Mexico form the basis of a sump- 

 tuous report by Messrs. Crosse and Fischer, wi o treat of the wliole 

 land and fresh-water fauna of the Republic in a manner which renders 

 their work indispensable to all students of the subject. 



A valuable and little known report on Mexican land shells was 

 issued in Hamburg bj^ Herr Hermann Strebel, assisted by Dr. G. 

 Pfefifer, and should be consulted by anyone who is investigating this 

 fauna. 



In the imi^ortant series of monographs by Messrs. Godmau and 

 Salvin on the biology of Central America, the mollusks are described 

 by Dr. E. A^on Martens, and those parts which ha^•e api)eared are of 

 that masterly character which the reputation of that author has long 

 led us to expect. 



Latest of all, and jiractically simultaneously with the work of the 

 Boundary Commission on wliich the i)reseut paper is based, may be 

 mentioned ex])lorations set on foot by the California Academy of Sci- 

 ences in northwestern INIexico and the peninsula of Lower California, 

 during which interesting collections were made by Messrs. Eisen, 

 Bryant, A^aslit, and others, Avhich have been reported on by Dr. J. G. 

 Cooper and partly discussed by the writer. 



The material collected belongs to three diiferent faunal regions of 

 very difierent degrees of interest, and each will be discussed separately. 

 These are: (1) the Central or Sonoran region, extending from the Rio 

 Grande of Texas to the Colorado River of Arizona, and on both sides 



