XVI PREFACE. 



it were difficult to know where to begin the reckoning. 

 The mention of this circumstance will serve to explain why 

 the number of fin-rays as stated in this work will be often 

 found to exceed the number given by former authors, who 

 appear in general to have made their computation without 

 much attempt at accuracy. The above remark, however, 

 does not apply to the caudal fin, in which, generally, though 

 not always, there is a tolerably well marked line of separa- 

 tion between what may be termed the principal rays, and 

 the accessory or shorter ones. In many instances, in 

 which this distinction is evident, these two kinds of rays 

 are reckoned separately. 



Appended to the description of each species, are a few 

 general remarks illustrative of its habits; more especially 

 those connected with locality, food, and propagation. It 

 was thought that these would render the work more gene- 

 rally useful. Many of them are the result of the author's 

 own observation, though some are confessedly obtained from 

 other sources. 



On the subject of Classification, it must be remarked 

 that the system of no one individual author has been rigidly 

 adhered to. Regard has been paid to what has been written 

 on this subject by the most recent writers in each department, 

 and all the larger groups, as well as, in most instances, their 

 mode of collocation, have been derived from such sources. 

 The arrangement of the Mammalia has been drawn up 

 from a combined view of the system of Cuvier, and the 

 systems of Gray * and MacLeay f. That of the Birds 

 from a similar view of the system of Vigors J, and the 

 modifications of that system as adopted by Swainson and 



* Ann. of Phil. vol. xxvi. p. 337. f Linn. Trans, vol. xvi. p. 1, &c. 



\ Linn. Trans, vol. xiv. p. 395. See also some Articles by the same author 

 in the first and second volumes of the " Zoological Journal." 



