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PREFACE. 
Tue Collection, from which the shells described in the 
following pages have been carefully selected, was made at 
Mazatlan, (Jat. 23° N., long. 1079 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) Dhat tt be preserved separate and 
intact, as a local collection: (2) That tt 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, 
&e., and 6368 Univalvés) mounted on 2529 glasstablets.* 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 with 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 
eut to any required size. To write the names, white paint sbould 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 corks of test tubes. 
