258 Miscellaneous. 



good characters. Charpentier states it to be the smallest European 

 Agrion he has seen (though it is not very much smaller than A. ele- 

 gans). I have one from the East Indies scarcely exceeding one half 

 in size. It seems strange that the female of A. aurantiucum, Longch., 

 figured by Mr. Curtis, should be unknown. 



There seems great uncertainty as to many species of Lihellulce de- 

 scribed by Linnseus, in consequence of his too great brevity. 



Lib. anea is given " thorace seneo-viridi," which w^ould have done 

 very well if no other allied species had existed ; but he gives as a 

 syn. from Fn. Suec, " thorace viridi nitido lineis Jiavis," which evi- 

 dently belongs to another species. He also refers as a syn. of L. ru- 

 bicunda (figured by Mr. Curtis) to Ray 50. n. 8, which I take to be 

 only L. vulgata. 



The continental authors seem at a loss for the L. rubicunda and 

 JE.juncea, both of which are in the Linn, cab., and I have taken 

 both in England. 



Moses Harris has figured in his ' Exp. Engl. Ins.' a fly which I take 

 to be the Criorhina apicata, Megerl., but which has been en-oneously 

 referred to C. ranunculi, both of which I possess now^ the former 

 having been taken near Bristol last year, and formerly at Stepney. It 

 is remarkable in its similitude to the Bombus hortorum. I have also 

 added Eristalis alpina, Pz., from Scotland lately. 



Glanville's WooUon, .-\pril 8th, 1842. 



WHAT CONSTITUTES A GENUS ? 



To the Editors of the Annals of Natural History. 



Gentlemen, — I should like to ask ornithologists, through the 

 medium of your valuable Magazine, what characters are sufficient 

 to constitute a Genus ? and if there be any rule for beginners to go 

 by ? or if every person who chooses to write a book on birds is at 

 liberty to make and mend as he thinks proper ? and thus add to the 

 general confusion — (this seems to be too much the case). I have 

 been attempting to arrange a small collection, but I am often brought 

 to a stand-still, as I cannot see the characters which have caused the 

 divisions ; for what seems to be sufficient in one case is not in an- 

 other. This has often caused me to wonder if there were a general 

 rule to go by ; perhaps G. R. Gray, Esq., or Mr. Strickland, will 

 favour me with answers to my questions. Mr. Gould seems to deal 

 largely in genera, — perhaps he may favour your ornithological readers 

 with an answer, if there are no secrets. 



I am, yours respectfully, 



Liverpool, March 24th, 1842. H. G. I. 



FURTHER REMARKS ON FIBRE. BY DR. MARTIN BARRY. 



Dr. Barry examined the following objects, from two of the Mol- 

 lusca, at the desire of Professor Owen, who dissected them out for 

 the purpose : namely, from the Oyster, the branchial ganglion, and the 

 branch connecting it with the labial ganglion ; from the Loligo, the 

 optic and brachial nerves. In all of these Professor Owen recog- 



