1y. PREFACE 
tablet inthe Catalogue. Of the minute specimens, magnified 
sketches are given, drawn under the microscope with Chevalier’s 
prism-dise. The principal part of the money required for the 
purchase of the shells has been generously and without solici- 
tation provided by Herbert Thomas, Esq. of Bristol. For the 
remainder, and for all the work, from the first sorting and wash- 
ing to the permanent allocation, (including no inconsiderable 
share in the manual labour of printing,) Iam alone responsible. 
The duty of writing the Catalogue was intrusted to me by 
Dr. Gray. I was ill fitted for it, (1) by almost entire ignorance 
of conchological literature, and (2) by living in a country town, 
with extremely limited aecess 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 materials. 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 reach.* 
I have endeavoured to make it a companion to Prof. C. B. Ad- 
ams’ extremely valuable Catalogue of the Shells of Panama, 
_which belong to the same great Tropical Fauna of W. America. 
An estimate of the value of the Reigen Collection as a 
geographical authority, and a comparison of it with other 
neighbouring faunas, will be found im the “Report of the pre- 
sent state of our knowledge of the Mollusca of the West Coast 
of N. America” presented to the British Association in Sept. 
1856. and published in its transactions, pp. 159 ef seg. The 
= In the course of the inquiry, I have met with the greatest kindness from 
naturahsts, most ef whom were previously unknown to me, but to whom I 
applied for assistance. To Hugh Cuming, Esq. lam under extraordinary obli- 
eations for his singular urbanity, in allowimg the unrestricted use of his mvalu- 
able collections. his Hbrary, 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 
Atisntic, the whale of his collections and notes from the W. American coast, for 
comparison with those known in this country. To Dr. Gray and R. M’Andrew, 
Esq. I am indebted for the long use of valuable works, and for advice and assist- 
ance throughout. Prof. Dr. Dunker, of Marburg, gave me valuable sid in the 
Mytilide, J. D. Gaskein. Esq. im the Cypreadz and Columbellicde, L. Reeve, Esq. 
in the Patelliide, W. Clark, Esq. and W. Bean, Esq. im the Cecide, J. Alder, Esq. 
in thst family and in Jeffreysiade, and Miss Steere in Olivide. 8. Hanley, Esq. 
sllowed me the use of his collection, (representing the Havre division of M. 
Reigen's stores,) and, slong with R. D. Darbishite, Esq. Dr. Baird, Messrs. 
H. & A. Adams, Rev. T. Hinmcks, S. P. Woodward, Esq. and F. Archer, Eaq. 
gave the benefit of eritical judgment and experience whenever solicited. I am 
aiso under great obligations to the 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 whose friendly 
encouragement mainly induced me to undertake the work, was, at its com- 
mencement, suddenly removed from the field of Isbour which was opening before 
him with such promise in the metropolitan university of Scotland. 
