2 BRITISH MARINE TESTACEOUS MOLLUSCA : 
South Devon coast at Exmouth, where I have passed my 
leisure in the dissection and examination of the Marine Tes- 
taceous Mollusca. Nearly every animal has undergone, in a 
living state, my personal examination, and in many species 
often repeated. I have had my own dredger, and I may say 
with some confidence, that there are few individuals who 
have had better opportunities of observing the organs, their 
functions, and the habitudes of these varied and interesting 
animals, than myself. I trust that my dissections and in- 
vestigations will give such a general, and in some measure 
particular account of their external configuration and internal 
anatomy as will suffice to furnish the younger students of this 
branch of zoology with some knowledge of their organization, 
and afford them sufficient aid to discriminate the organs of 
the animals, so as to let none pass without careful observation ; 
for how many curious creatures, which perhaps only occur 
once in a lifetime, have been overlooked for want of such 
assistance, and are for an indefinite time lost to science! I 
speak with deep regret on this pomt; as in my earlier career 
I have neglected opportunities that have never occurred since, 
and which I have felt the loss of. 
The anatomies of Pholas dactylus, Teredo megotara, Denta- 
hum tarentinum, Bulla hydatis, and other desultory anatomical 
observations by myself, with references to M. Cuvier, the 
“principium et fons” of faithful comparative anatomy, will 
sufficiently explain the structure of the Acephala and Gastero- 
poda that have been treated of in these memoirs ; which are 
by no means to be considered as strictly local ones. Though 
the species have been obtained from one vicinity, they will be 
found to give, I hope, a faithful portraiture of most of the 
animals of the entire class of the British marine testaceous 
Mollusca. There are, however, gaps which it has never been in 
the power of malacologists to fill up; but the hope of acquiring 
the rare desiderata ought not to be considered as forlorn. I 
have lately fallen in with very unexpected acquisitions which 
afford a practical illustration of the quotation— 
*Turne, quod optanti Divum promittere nemo 
Auderet, volvenda dies, en! attulit ultro.”’ 
