ON MOLLUSCA OF THE WEST COAST OF NORTH AMERICA. 163 



Triton has been dredged with the animal in, off the coast of Guernsey*. 

 It is therefore very desirable that collectors should have a general acquaint- 

 ance with the shells of a variety of distinct provinces, in order that they 

 may be prepared to detect errors when they arise. For this purpose also 

 the formation of local collections in public museums is very greatly to be 

 recommended f. 



9. It might be thought that all sources of error would be avoided, when 

 competent naturalists themselves collect shells in their original haunts. But 

 when different places are visited, it is not always possible, in the confinement 

 of a ship, or amid the confusions of land travelling, to pack and tabulate 

 accurately the results of each branch of inquiry : or, supposing these errors 

 guarded against, intermixings may still take place in the unpacking and dis- 

 tribution of specimens. Moreover, when shells are left loose in cabinets, 

 and the information is supplied by ticket only, a variety of interchanges may 

 very unexpectedly take place. Such errors are most serious when they take 

 place in the collections of naturalists deservedly noted for their accuracy; 

 because whatever appears in their cabinets is naturally regarded as of un- 

 questionable authority. Thus, a Ceylon shell ran an imminent risk of being 

 described as from Mazatlan ; and specimens were found bearing one locality 

 on the ticket affixed to them, and another on a ticket within. Thus, also, 

 Prof. Adams notes \ having received a Pleurotoma zonulata from Mr. 

 Cuming, as from the Philippines. Indeed, after the vast collections made 

 by that gentleman in so fruitful a locality, it was natural that shells should 

 be often assigned to this habitat, unless a contrary were known. The " China 

 Seas" or " Eastern Seas" of Lieut. Belcher are also supposed to have in- 

 cluded many chance acquirements; among others, Dosinia Dunkeri from the 

 Panamic, and Semele rubro-lineata (= simplex) from the Californian fauna. 



10. All these errors, from whatever source derived, find their way into 

 the monographs, sometimes with additions by the writers themselves, and so 

 become perpetuated. Some authors, even in our own country as well as in 

 France, are not strict in regard to geographical boundaries. " Central 

 America" and "West Columbia" are used generally for the tropical portions 

 of the W. American coast, and " California" for any stations north of Aca- 

 pulco, either in the Panamic or the San Franciscan province. Mr. Reeve, 

 indeed (under Patella venosa, pi. 10. f. 18), extends W. Columbia south- 

 wards to include the Isle of Chiloe, in lat. 4-3°, just as Valenciennes and 

 Kiener extend Peru northwards to include Acapulco. By mistake, Mr. Sow- 

 erby, jun., refers a Panama shell to Jamaica, when he cites Prof. Adams's 

 Cerithium validum, and gives as the habitat of Pattella nana and albofasciata, 

 P. Z. S. 1841, p. 52, "ad insulam Panama, Philippinarum." 



11. Another class of errors arises from confounding places which bear 

 the same name. Thus St. Vincent's may be either the island in the West 

 Indies or on the Guinea coast, according as it is used by Guilding or Tarns. 

 San Bias may be either the near neighbour of Mazatlan in the Gulf district, 

 or it may be D'Orbigny's locality in Patagonia. And San Juan may be 

 either the bay on the Gulf side of the Peninsula of California, in lat. 27°, or 

 the Straits of San Juan de Fuca (or Fuaco), near Vancouver's Island. It is 

 believed that in Kellett and Wood's collections, the words de Fuca havp 



* Some may attribute a solitary specimen of Trochus conulus found by Mr. Bean at Scar- 

 borough to a like importation. 



f Prof. E. Forbes had been collecting materials for a series of such collections at the University 

 of Edinburgh. It is hoped that they may yet be made available for the purposes for which 

 they were designed. 



X Pan. Shells, p. 144 ; so also Omphalitis Californicus, ticketed " Moreton Bay," Mus. Cum, 



m2 



