2 BEITISH MAKINE 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 point ; 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- 

 lium 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 tlie 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." 



