iSgi.] 



THE BRITISH NATURALIST, 



^3 



This finishes the changes in the land shells that seem worth notice ; 

 later, the fresh-water species will have to be considered. — T.D.A.C. 



Shells near Doncaster. — The following shells occurred all in or 

 hy one pond at Adwick, near Doncaster, on June i6th, 1887 



Succinea ptitris, S. elegans^ v. minor, LimncBa pefegva, L. truncatula, 

 L. tvuncaUila, v. elegans, L. palustris and vars. alhida (two), tincta 

 (several), and laciinosa ; Bytliinia teutaciilata, Physa hypfiorum, Planorhis 

 spirorbis, and monst. scalarifornie, P. complnnatus and var. rhomhea, 

 P. vortex, Lininosa glabra, Pisidiuin (two species). Helix nemoralis on 

 the edge of the pond. — Geo. Roberts. 



Vertebrata. 



"WHAT IS A BIRD ? " 



BY LINN.'EUS GREENING. 



What is a bird ? is one of those simple questions which are far 

 easier to ask than answer. Some would say it is an animal that can 

 fly ; true, but other animals than birds possess this power, as, for 

 instance, bats and the majority of insects, so this definition is not 

 satisfactory. Besides, we must remember that there are many birds 

 which cannot fly, such as penguins amongst sea-birds, and the ostrich 

 amongst land ones. To begin at the beginning of an animal's life is 

 the best way to get at its proper position amongst the multitudinous 

 forms of life that have existed, and now exist, around us. Our re- 

 searches will take us back far away to a time when our present species 

 were not yet formed, and when, indeed, such animals as birds had, 

 strictly speaking, not yet appeared. 



How then, and by what wonderful process have these beautiful 

 beings come into existence ? Ages ago, in the carboniferous period, 

 when our present coal-beds were tropical forests and jungles, inhabited 

 by a fauna markedly different from any that have since existed. The 

 highest living animal was a kind of newt, at least an animal which 

 was of such curious structure that it is hard to say whether it was a 

 newt or a reptile. Of course, if we wished, we might go still further 



