In the observations appended to the characters of groups and species, there is added, as opportunities occurred, a physiological account of the mode of formation and structure of the different parts of shells.* It is to this part of the subject that I would especially direct the attention of my readers; as, in the study of the structure, formation, developement, and colouring of the shells, and in the habits of the animals. which form them, they will find a never-failing source of pleasure and instruction, which can be carried on without any expense. For these particulars are as easily to be observed in the most common snail, as in the finest and most expensive shells in the cabinets of the curious; and the details are more easily followed out, from the very fact of the facility of observing many specimens at the same time, in different states of developement: so that, to the philosophical conchologist and reflecting student, the most common specimens may do more to illustrate the perfection and all-seeing wisdom of the Creator, than the most costly collection. the description of the species, particular attention has been paid to dividing them into small groups, to facilitate their determination; and an attempt has been made to point out the different varieties that occur, not by describing each individual variety that may be found, but by indicating the points that have

In

* For a larger exposition of my views on this subject, reference should be made to papers published in the Philosophical Transactions for 1833, and in the first volume of the Zoological

been observed to be most liable to variation, and also the monstrosities which, from the mode of formation of the shell, and some peculiarities in the habit of the different species, are likely to take place in each of them. To illustrate the animals of the different families and genera, a series of vignettes has been given; and further to assist in determining the species, some wood-cut figures of the shells have been interspersed in the text.

All the new species introduced into the work, and the more remarkable varieties, have been figured, and added to the plates (except Vertigo angustior, which could not be procured); and the whole of the figures which were given in the former edition have been compared with the specimens, and corrected where required. There have also been added to these plates other figures of the same species, and enlarged details of those parts of the smaller kinds which are calculated to facilitate the determination of the species. Indeed, although this work has been called in the titlepage a new edition of Dr. Turton's Manual, it may be almost considered a new publication, as the only portions of the former edition that have been retained are the descriptions of the species, and a few of the general observations; in so much that, on revising it in its printed form, it is a matter of regret to me, that it was not rather undertaken as an entirely new work, which would not have cost me nearly so much trouble as editing the present one.

I have only further to return my thanks for the

kind and friendly assistance which I have received from Mr. Jeffreys, Mr. Hincks, Mr. Philip Carpenter, Mr. D. Cooper, Mr. Carter, and especially from Mr. Thompson of Belfast, and Mr. Alder of Newcastle, who have kindly sent me specimens for comparison and figuring. Some apology is, perhaps, due to those who have been expecting the new edition of the work which has been so long advertised: this has partly been occasioned by the delay in the completion of the plates, and partly by numerous engagements, which have only allowed me to pay attention to the subject at leisure moments, when not occupied by my official duties.

Eliot Vale, Blackheath,

Feb. 12. 1840.

90, 91. 93, 94. 97, and 98. for "t. 8 read "t. 10."

127. line 19. add "t. 11. f. 129."

133. line 3. add "t. 11. f. 130."

135. line 5. for "f. 24." read "f. 34."

139. line 7. for "31." read "t. 11. f. 131."

175. line 22. for "t. 4. f. 39." read "t. 12. f. 138."

200. line 28. for "t. 140. f. 10." read "t. 12. f. 140."

205. at bottom, erase "f. 142."

221. line 20. add " (t. 7. f. 77.) "

227. line 26. add “t. 12. f. 146.”

234. add to var. “t. 10, f. 101.” a. b. d.

239. line 4. for "pulustris," read “ palustris."

N. B. As the plates were not returned from the engraver until the greater part of the text was printed, there are unfortunately the above errors in the references to the figures in the text, and a few references to them have been left out; but these can be easily added by the pen, space having been left for the purpose.