162 report — 1856. 



man Mr. Nuttall, incomplete as it is, remains the best list of that interesting 

 district ; and in spite of the old-established English settlement near the 

 Columbia River, it was left to the United States' Exploring Expedition to 

 make us even moderately acquainted with the shells of the Oregon district. 

 Of the abyssopelagic species in Oregon and California, we have only the 

 very limited collections of Belcher and Hinds ; and of the minuter forms, 

 which in the British fauna are 31 per cent., in the Panama fauna 13 p.c, and 

 in the Mazatlan fauna no less than 39 p. c. of the whole number of species, 

 we cannot reckon more than half-a-dozen names. 



6. It might be thought that, in order to obtain suitable lists of the Mol- 

 lusca inhabiting particular localities, all that was necessary would be that 

 shells should be brought from that locality, and then described. But such 

 is far from being the case. A few of the principal causes of error, both as 

 regards habitat and description, will be noticed, in order that suitable cau- 

 tion may be observed in judging of the materials to be presented. 



1. Errors respecting habitat. — A large part of the shells in collections have 

 been brought from the seats of trade. Either persons at home, in their com- 

 munications with friends at sea-ports, request that shells may be sent back ; 

 or sailors bring them as an article of commerce. In both cases, the greatest 

 number of specimens is collected from all sources, and no dependence what- 

 ever can be placed on the results. Thus, well-known East Indian, Philip- 

 pine, and Polynesian shells have been sent from Acapulco and Mazatlan ; 

 and coast shells from various latitudes, including the Sandwich Islands, 

 occur in the Oregon collection of Lady K. Douglas. It is well if sailors and 

 captains do not add to the confusion by mixing together shells picked up at 

 different places on the voyage. Nor do the errors end here. When they 

 pass into the hands of dealers, it is rarely that the least attention is paid to 

 their locality. They are mixed in drawers in every possible confusion, and 

 instances have not been rare of traders coining habitats to suit the supposed 

 taste of their customers. Even when they have their eyes open to the im- 

 portance of accuracy, such are the circumstances of confusion attendant on 

 the management of their business, that correctness is rarely to be ex- 

 pected. 



8. But even if collections have been made on a single spot by a traveller 

 of ordinary and even of conchological attainments, errors may arise from 

 shells imported in ballast, &c, and dropped on the shore. Adhering and 

 burrowing littoral shells may thus be found alive in places foreign to their 

 native seas. This may account for a specimen of Acmcea pelta, abundant at 

 Oregon, being found with the Mazatlan Limpets ; and for Littorina aspera 

 being given by Prof. Forbes in his zoological map as the characteristic spe- 

 cies of the Oregon instead of the Mexican fauna, specimens having probably 

 reached the northern collectors in the same way. As an aid to detect these 

 errors, it is very desirable that shells should be retained without being sub- 

 jected to the usual acid treatment, as the accretions, or the minute shells 

 among the dirt, will often decide a point that the shell itself will not deter- 

 mine. Thus, a small specimen of Fissurella Barbadensis was separated from 

 a boxful of F. virescens (a variety of which in the young state it closely 

 resembles) by a minute Spirogli/p/ius and coral which seem peculiar to the 

 Atlantic Seas. Thus also specimens of Ostrea iridescens with their Placu- 

 nanomice were confirmed in their African habitat, from the minute shells 

 between the laminae, which agreed with the African and differed from the 

 Panamic types. How many of these ballast species have found their way 

 into the well-searched British shores, is patent to the readers of Forbes and 

 Hanley's Hist. Brit. Moll. It is said that even the great Mediterranean 



