24 [Senate 



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

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

 tablet in the Catalogue. Of the minute specimens, magnified sketches 

 are given, drawn under the microscope with Chevallier's prism-disc. 

 The principal part of the money required for the purchase of the 

 shells has been generously and without solicitation provided by 

 Herbert Thomas, esquire, of Bristol. For the remainder, and for 

 all the work, from the first sorting and washing to the permanent 

 allocation (including no inconsiderable share in the manual labor 

 of printing), I am alone responsible. 



The duty of writing the Catalogue was intrusted to me by Dr. 

 Gtay. I was ill fitted for it, (1) by almost entire ignorance of con- 

 chological literature, and (2) by living in a country town, with 

 extremely limited access to scientific books and collections. There 

 did not appear, however, any competent naturalist who possessed 

 the absolute essentials of time and full access to the Mazatlan mate- 

 rials. I therefore undertook the task, trusting that its acknowledged 

 deficiencies might in some measure be compensated for by great 

 patience and care in the faithful use of those means of information 

 which were within my reachf . I have endeavoured to make it a 



* 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, with- 

 out 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 collec- 

 tion are cemented with canada balsam to strips of thin glass, which are fastened into the corks of 

 test tubes. 



f In the course of the inquiry, I have met with the greatest kindness from naturalists, most of 

 whom were previously unknown to me, but to whom I applied for assistance. To Hugh Cuming, 

 esquire, I am under extraordinary obligations for his singular urbanity, in allowing the unre- 

 stricted use of his invaluable collections, his library, and his original information to a complete 

 stranger. Dr. A. A. Gould, of Boston, U.S., intrusted to my care, and to the perils of the At- 

 lantic, the whole of his collections and notes from the West Americau coast, for comparison with 

 those known in this country. To Dr. Gray and R. M« Andrew, esquire, I am indebted for the 

 long use of valuable works, and for advice and assistance throughout. Prof. Dr. Dunker, of 

 Marburg, gave me valuable aid in the Mytilidse; J. D. Gaskoin, esquire, in the Cypraeadae and 

 Columbellidae ; L. Reeve, esquire, in the Patellidae ; W. Clark, esquire, and W. Bean, esquire, 

 in the Caecidae ; J. Alder, esquire, in that family and in Jeffreysiadae, and Miss Steere in tho 

 Olividaa. S. Hanley, esquire, allowed me the use of his collection (representing the Havre 

 division of M. Reigen's stores), and, along with R. D. Dareishire, esquire. Dr. Baird, 

 Messrs. H. & A. Adams, Rev. T. Hinx'ks, S. P. Woodward, esquire, and P. Archer, esquire, 

 gave the benefit of critical judgment whenever solicited. I am also under great obligations to tho 

 officers of various public museums and libraries, for the kindness with which they have attended 

 to my requests. One whose promised aid would have been of invaluable service, and whoso 

 friendly encouragement mainly induced me to undertake the work, was, at its commencement, 

 suddenly removed from the field of labour which was opening before him with such promise in 

 the Metropolitan University of Scotland. 



