370 Bibliographical Notices. 



hibit, when correctly spelt, a difference from all preceding ones, 

 though it amount only to a single letter. 



At the same time, the principle proposed by Mr. Gray should ope- 

 rate as & caution to naturalists, when constructing new generic names, 

 to avoid, as far as possible, such terms as closely resemble those al- 

 ready adopted. 



The number of generic groups enumerated in this work amounts, 

 as before stated, to 1119. It is to be hoped that this number will 

 in future be increased only by the discovery of new forms. It is 

 after all a mere matter of taste, how far the process of forming new 

 genera by subdividing old ones shall be carried. Subdivide as we 

 may, the diversities of structure will never be exhausted until each 

 species is made into a genus, for there is rarely an instance of two 

 species, however closely allied, that precisely agree in the proportions 

 of all their parts. We may therefore cease from subdividing when 

 we think that the limit of convenience has been attained ; and most 

 persons will admit that it has been reached, if not exceeded, in the 

 case before us, where about 5000 species (for no more are known 

 with accuracy) are distributed into no less than 1119 genera. Mr. 

 Gray is of opinion that these genera might be advantageously con- 

 densed to the number of about 800, and in this I quite agree with 

 him. 



The systematic classification adopted by Mr. Gray is considerably 

 improved in this edition, though there are still several groups which 

 I think might be better arranged. Most of these cases were pointed 

 out in my former commentary ; and as the question of affinities is, in 

 the present state of our knowledge, in great measure open to opi- 

 nion, it is very natural that Mr. Gray's views should occasionally differ 

 from mine. 



The alphabetical index is a valuable appendage to the present edi- 

 tion, but one thing is still needed, a list of the books which have 

 been consulted in compiling this work. Many of the authorities for 

 genera have been extracted with great perseverance from works of 

 extreme rarity in this country, and it would have been a great aid to 

 the student if the titles of these works had been enumerated in Mr. 

 Gray's book. I would suggest that this defect might be in some 

 degree supplied if Mr. Gray would send such a list to this Magazine. 



I now proceed as before to remark on the details of Mr. Gray's 

 volume, but it will be seen, that from the far greater accuracy of the 

 present edition, my criticisms will be much less numerous than on the 

 former occasion. 



At page ix of his preface, Mr. Gray states, through an oversight, 

 that the number of genera of birds in Linnaeus' last edition is 104, 

 when in fact they are 78. It follows that the calculations deduced 

 therefrom are erroneous. The proportion of species to genera in the 

 ' Systema Naturae' will be twelve to one, not nine to one. 



Page 7 of the text. For the reasons above stated, I trust that the 

 name Scops will be retained for the genus of Owls which has so long 

 borne it, in which case the type should be called Scops zorca (6m.), 

 not Scops aldrovandi, Bon. 



