16 Panama Shells. 



INTRODUCTION. 



Mazatlan ; Dec. 21 to Dec. 27 at San Bias ; Jan. 8, 1838 to 

 Jan. 23 at Acapulco ; May 10 to June 1 at Callao ; June 5 to 

 June 17 at Payta ; June 23 to July 3_at the Gallapagos. The 

 Atlas de Zoologie of this expedition, (pub. 1846) contained 24 

 folio plates, of shells and mollusca. The text we have not 

 seen. 



In 1839 the U. S. Exploring Expedition touched at Callao, 

 which was the only place in this zoological province, that was 

 visited by the expedition. About 30 species of shells were 

 collected, of which four new species have been described by 

 Dr. Gould in the Proceedings of the Boston Society of Natural 

 History since 1846. 



In the Zeitschrift fur Malakologie of Aug. 1847, Dr. K. 

 T. Menke commenced a catalogue, with descriptions of the 

 new species, of the shells of Mazatlan. These shells were 

 collected by Mr. Henry Melchers of Bremen, who has spent 

 several years in Mazatlan. Additions have since been made 

 to the catalogue, and up to Feb. (inc.) 1851, Dr. Menke has 

 catalogued 173 Mazatlan species. Of these 26 are described 

 as new species, not including a few which were proposed as 

 new but have since been identified by Dr. Menke with pre- 

 viously described species, 



At the present time Dr. Gould is engaged in the exami- 

 nation of species, which have been collected at various points 

 between San Francisco and Mazatlan, These collections were 

 made by Maj. William Rich, and Col. E.< Jewett, U. S. A, ? 

 and by Lieut. Thomas P. Green, U. S. N. They are the more 

 important, because they come from regions intermediate be- 

 tween two great zoological provinces, and we may hope there^ 

 fore that Dr. Gould Will show, with as much precision as the 

 i'acts themselves will admit, the boundary between them. At 

 a meeting of the Boston Society of Natural History, Septem- 

 ber 3, 1851, Dr. Gould read descriptions of 17 new species of 

 Acophala from these frontier regions. The collections 



