251 
REVIEWS. 
BRITISH CONCHOLOG Y."- 
T the commencement of his volume, Mr. Jeffreys refers to the ex- 
pensive character of the “ British Mollusca,” by Professor E. 
Forbes and Mr. Hanley, as a reason for his having undertaken the present 
work. No such apology was needed : naturalists who know anything of 
the enthusiasm of the author for his subject, and of the zeal with which, 
for many years, he has devoted himself to his favourite study, would 
have had cause for much regret if the materials thus collected had been 
withheld from the public, or were only to be found scattered in the many 
communications made by him to various scientific societies. 
To afford some idea of the research undertaken in preparation for the 
present work, we may refer to the author’s account of his investigations 
relating to a single genus of small fresh-water bivalves : — 
“ My own cabinet contains no less than 274 parcels of Pisidia, which 
have been in the course of the last thirty or forty years collected from 
different localities and sources, and comprise many thousands of specimens. 
I have personally examined the types of those species which have been 
described by Dr. Turton, Mr. Jenyns, Mr. Alder, Dr. Bandon, and other 
concliologists who have published on the subject. I have collected these 
tiny shells in many parts of Holland, Germany, France, Switzerland, 
and Italy, for the sake of comparison with British forms ; and I have 
had to refer to numerous works in many languages in order to collate 
the descriptions of forty-one different species which have been proposed 
by European writers within the last century. Of these I cannot con- 
scientiously recognize more than six as distinct.” 
Although the volume now published is confined to land and fresh-water 
shells, the Introduction, extending to 114 pages, is quite general, and 
affords space for the description, in a very readable form, of most of the 
questions interesting to concliologists. Without expressing a decided 
opinion on the “ origin of species,” Mr. Jeffreys suggests a practical method 
of distinguishing between species and varieties. He says : — 
“ I believe it may now be considered a well-established rule that all 
distinct groups of individuals, living together, and having a common 
feeding-ground, and which are not connected or blended with each other 
by insensible gradations, are prima facie entitled to the rank of species.” 
* British Conchology . Parti. — Land and Fresh- water Shells. By John 
Gwyn Jeffreys, F.R.S., &c. Van Voorst. 18(12. 
s 2 
