INTRODUCTION. 3 
varieties of it. At least six good (?) species have emerged 
from the varieties of Lamarck’s shell: N. lyrata, Marrat, is the 
lyrate form; N. tricarinata, Lam., is the carinated form; N. sculpta, 
Marrat, is another ; N. sistroides, Neville, N. trinodosa, Smith, and 
N. corticata, A. Ad. Another variety occurs showing a close 
affinity with the N. muricata, Quoy and Gaim., and the shell figured 
in Reeve’s Conchologia Iconica as the N. vibex, Say, is a spiny 
form. Some of the shells from Ceylon are very closely connected 
with varieties of the N, Gruneri, D’k’r., and others with smoother 
ribs to the N. Jacksoniana, Quoy and Gaim. 
In the preface to Wood's Catalogue of Shells, published in the 
year 1828, we find the following remark: “It has, therefore, been 
the endeavour of the author, in the absence of larger and more 
costly publications, to supply their place by a work which will 
incorporate in one volume figures of all the known shells.” From 
the statement here quoted the number of shells known to concho- 
logists at this date amounted to about two thousand. A little 
more than fifty years have elapsed, and we find that the numbers 
have increased to at least thirty thousand. Suppose we recommend . 
the study of a single genus to each of our conchological students ; 
if the success attending their efforts be in proportion to those re- 
sulting from the study of the Nassz, before this century expires we 
will have at least five hundred thousand shells) We may name 
these shells and describe them as distinct, but they will not be so after 
we have finished ; on the contrary, we may adopt another plan and 
name them varieties, but the same objection continues ; the variety 
we have named as coming from any locality will be found to differ 
from the shells brought up from the same ground by the next haul 
of the dredge. It is a very disagreeable task to be compelled to 
state that the starting point of the systematist, upon which the 
whole fabric is built up, is wrong, and the whole of the deductions 
drawn from this source are erroneous; nevertheless, I am compelled 
to utter that which I believe to be strictly and unquestionably true. 
I cannot expect the conchologists, who are totally unacquainted 
with the materials upon which I have based my deductions, will be 
found to coincide with my views, If they had studied the genus 
