vl INTRODUCTION. 
The general limits adopted for the whole fauna are the political frontier of Mexico 
in the north and of that of the State of Panama in the south, not on account of 
these being really natural, but because clearly-defined boundaries were needed. The 
Peninsula of California has been excluded by the Editors as not coming within the 
scope of their work, though its Molluscan fauna does not appear to be very different 
from that of N.W. Mexico; no new material from that region was, however, available 
for examination. The Tres Marias Islands, belonging politically to Mexico, are 
included, as well as Utila and Bonacca, in the Bay of Honduras. <A few forms 
from Cocos Island, situated between Panama and the Galapagos Is., and belonging 
politically to Costa Rica, are noticed, chiefly for the purpose of figuring two of 
H. Pittier’s novelties from that place, one of them being allied to a Nicaraguan form ; 
its fauna, however, has, on the whole, a somewhat Polynesian character. 
On the Plates, of which twenty-eight coloured and sixteen uncoloured have been 
required, I have endeavoured to figure not only the new species, but also those 
previously described that had not been satisfactorily illustrated before. The present 
Volume, with the above-mentioned works of Fischer and Crosse and Strebel, both 
indispensable to the student of the Mexican and Central-American Mollusca, will 
therefore include a figure of nearly all the known species of these regions. Moreover, 
I have in many cases given figures of the young state, or of individual variations, 
chosen from a large number of specimens obtained at the same locality, to show the 
various forms of the same species. 
The historical development of our knowledge of the Mexican and Central-American 
Mollusca having been. somewhat fully exposed by myself in the ‘ Malakozoologische 
Blatter, xii. pp. 1-4 (1865), and, at greater length, by Fischer and Crosse in the 
** Mollusques ” of the ‘ Mission Scientifique en Mexique et dans Amérique Centrale,’ 
i. pp. 2-9, and ii. pp. 655, 656, I shall here confine myself to some remarks concerning 
the travellers whose collections have chiefly contributed to my own work on the 
subject. 
MEXICO. 
FerpinanD Depp, a gardener of Berlin, accompanied, in 1824-25, Count von Sack 
in his voyage to Mexico. He lived chiefly at Vera Cruz, Jalapa, and the City of 
Mexico, and remained independently in the country until 1827. In the followine 
5 
year he went again to Mexico, with Dr. Chr. J. W. Schiede, for the purpose of 
collecting plants and other objects of natural history, returning to Berlin, after the 
