PREFACE. 



THE Collection, from which the shells described in the 

 following pages have been carefully selected, was made at 

 Mazatlan, (lat. 23 1ST., long. 107 W.) during the years 1848-50, 

 by a Belgian gentleman named Frederick Reigen. The bulk 

 of it was sent to Liverpool for sale in 1851, and circumstances 

 enabled me to make a searching examination of it. Dr. Gray 

 having requested that the (comparatively) small selection 

 which I had made for my own use should be deposited in the 

 British Museum, I judged it conducive to the interests of 

 science to obtain possession of the whole of the then-remaining 

 stock, which was about to be dispersed ; and to select as many 

 specimens as might be required (1) to illustrate the local-fauna 

 of a known station at the mouth of the Gulf of California ; 

 and (2) to exhibit the amount of variation, whether great or 

 little, observed in comparing together large numbers of in- 

 dividuals in the various species. The latter object appeared of 

 no slight importance, especially for the sake of inland natural- 

 ists ; who have usually to depend on the very limited number 

 of specimens which are generally to be seen in public, still 

 more so in private collections. 



The series of shells here enumerated is presented to the 

 Trustees of the British Museum, and accepted by them, on the 

 following conditions : (1) That it be preserved separate and 

 intact, as a local collection : (2) That it be always open to the 

 use of students, subject to the usual conditions: (3) That the 

 donor be allowed to arrange the collection in its permanent 

 place of abode : and (4) That a Descriptive Catalogue of it be 

 printed under the direction of the Trustees. 



The collection consists of about 8873 specimens (2505 Bivalves, 

 &c., and 6368 Univalves) mounted on 2529 glass tablets.* The 

 number to the left refers to the species, that to the right to the 



* The following are the advantages of this mode of preserving specimens, 

 either in public or private collections. (1) Both sides of the shell can -be seen ; 

 thus combining the advantages of mounting vvith those of leaving loose. (2) The 

 drawers or cases can be lined with any coloured paper that happens best to 

 display the particular series. Very dark purple or black, glazed, will generally 

 be found most suitable. (3) The tablets and shells can be cleaned as they stand, 

 without remounting. (4) The tablets are extremely cheap, and can be rapidly 

 cut to any required size. To write the names, white paint should be worked 

 with a pestle in a little turpentine, till it is thin enough to pass through a fine 

 steel pen. The strongest cement is common shell-lac dissolved in spirit; but 

 the bleached liquid glue has a better appearance. The minute shells in the col- 

 lection are cemented with Canada balsam to strips of thin glass, which are 

 fastened into the corka of test tubes. 



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