T. Bland 071 the Geographical Distribution of Mollusca. 401 



Professor Adams, in his catalogue of Panama shells, carefully 

 adds the stations, and habitat of each species, from the authori- 

 ties to which he refers in its synonymy,^ as well as from his own 

 experience,! and distinguishes original, from other testimony. 

 He remarks in the Introduction, " on errors respecting the habitat 

 of species," from which we subjoin extracts, — we refer our read- 

 ers to the work itself for various useful illustrative notes. 



" Those who are famihar 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 ac- 

 cuse 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 verbal communication of statements respect- 

 ing habitat, naturalists at home are of course subject to all the 

 mistakes which the original collectors have made. These per- 

 sons often mix the collections made in various places, and depend 

 on memory for the localities, although they are often unable to 

 distinguish the species when placed side by side. 



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

 the writers themselves. When v/e see a marine species affirmed 

 to inhabit the Mediterranean, Senegal, the Indian Ocean, New 

 Holland, &c., we may often suspect the error to arise more or less 

 from erroneous testimony. But when one species is referred to 

 two distinct zoological provinces, which are known to contain 

 analogous but not identical species, we must sometimes suspect 

 the author of confounding such species." — p. 24. 



" For all these causes of error there is but one remedy, and 

 that is not infallible. Rejecting the testimony of careless and 

 incompetent observers, and all hearsay testimony, we must rely 

 on the testimony of competent observers. We may hope for 

 accuracy when they shall remember, that a very few errors may 

 essentially change the aspect of the plan of distribution, and pre- 

 vent all correct generalizations." — p. 25. 



It would be unfair to withhold a statement of the opinion of 

 Dr. Binney on this branch of our subject. His chapter in the 

 work previously mentioned, we refer to vol. 1, chap, iii, entitled 

 " Of some of the obstacles impeding the study of zoology, and 

 the means of overcoming them," is unquestionably replete with 

 interest. In his comments, contained in that chapter, on the hy- 



* The plan piirsued by Professor Adams as regards synonymy, is worthy of uni- 

 versal adoption. The synonyms are arranged in chronological order, and the dates 

 of the authorities referred to are added. 



f Station, says Lyell, speaking of plants, indicates the peculiar nature of the 

 locality where each species is accustomed to grow, — by habitation is meant a general 

 indication of the country where a plant grows wild. The terms so defined, he adds, 

 express each a distinct class of ideas, which have been often confounded together, 

 and which are equally applicable to zoology. — Principles of Geology/. 



