24 Panama Shells. INTRODUCTION. 



distributed. We have been under obligations, which we ac- 

 knowledge with much pleasure, to Dr. A. A. Gould, of Boston, 

 and to John H. Redfield and Robert L. Stuart, Esqrs., of 

 New- York City, for the use of books ; also to the librarians 

 of the Boston Athenaeum, of Harvard University, of the Acad. 

 Nat. Sciences, of Philadelphia, and to Dr. Henry Wheatland, of 

 the Essex Institute in Salem ; chiefly have we been indebted 

 to the nearly complete zoological library which Drs. T. B. and 

 Edward Wilson have presented to the Academy of Natural 

 Sciences of Philadelphia. 



On Errors Respecting the Habitat of Species. 



Those who are familiar with the frequency and 

 magnitude of the errors, which occur in the works of 

 the most celebrated authors respecting the habitats of 

 species, will not probably accuse us of presumption for the 

 little ceremony with which we have treated such statements. 

 Hearsay testimony has often been received without sufficient 

 scrutiny. In addition to the errors likely to occur in the ver- 

 bal communication of statements respecting habitat, naturalists 

 at home are of course subject to all the mistakes which the 

 original collectors may have made. These persons often mix 

 the collections made in various places, and depend on memory 

 for the localities, although they are often unable to distin- 

 guish the species when placed side by side.* 



Another class of errors, we fear, must be laid to the charge 

 of the writers themselves. When we see a marine species 

 affirmed to inhabit the Mediterranean, Senegal, the Indian 



* Thus we have received from an intelligent shipmaster, who was accustomed 

 to collect for a cotichologist, specimens of Cyclostoma^flavidum, with the positive 

 assurance that they were collected in a spot well known to us, not far from King- 

 ston, Jamaica. Yet the species occurs only in Porto Rico, while the locality in 

 Jamaica contains a Cylindrella of similar aspect. We may be allowed to mention 

 also an illustration of the manner in which mistakes of locality and not of species 



