322 Mr. J. \V. Kirkby on Permian Entomostraca 



For the convenience of those who may find fossil Entomos- 

 traca, or other small organisms, in a similar matrix to that in 

 which the Tunstall specimens occurred, it may be well to add a 

 word or two as to the mode I adopted for extracting the Permian 

 specimens from the calcareous dust. I first sifted the dust of 

 all the coarser particles — of everything larger than the tenth of 

 an inch ; and from what was left I took all the very fine dust 

 with another sieve, leaving a residue among which everything 

 organic could easily be distinguished. In picking out the or- 

 ganisms, a piece of polished slate — a common school slate, for 

 instance — is a good area on which to strew a portion of the 

 residue for examination. It is much better to adopt this method 

 than to pick the specimens out of a mass of material ; for by 

 sprinkling a small portion over the slab, every individual particle 

 can be recognized, and the organic forms separated from the 

 inorganic with very little trouble. A pair of blunt forceps with 

 broad points are exceedingly useful for picking up the specimens. 

 Some care is necessary, or injury may result to the specimens ; 

 but, with caution and a little skill, the forceps can be used with 

 a great delicacy of touch, and with less risk than the fingers. 

 Dr. Carpenter recommends the use of the moistened tip of a 

 cameFs-hair pencil in similar cases; and in instances where the 

 objects sought are extremely delicate, it will be the more prefer- 

 able instrument : but when the specimens, like the Permian 

 Entomostraca, possess a moderate degree of firmness, they may 

 be extracted with greater ease and celerity as above indicated; 

 and when an extensive series of examples is needed, expedition 

 is of some value. With the assistance of a common lens and a 

 pair of moderately good eyes, nothing more is required. It is 

 perhaps best to pick out a quantity of specimens " in rough," 

 and separate the specific forms afterwards. 



Genus Cythere, Miiller. 



Subgenus Bairdia [M'Coy], Jones, Entomostraca of the Cre- 

 taceous Formation of England. 



Syn. Genus Bairdia, M'Coy, 1844, Syn.Char. Carb.Foss. of Ireland. 



This group was instituted by Prof. M'Coy in 1844 for the 

 reception of two species of Entomostraca from the carboniferous 

 rocks of Ireland, which he considered to differ generically from 

 any existing genus*. 



Mr. Rupert Jones, in his Monograph of the Entomostraca of 

 the Cretaceous Formation of England, 1848, proposed its adop- 

 tion as a subgenus of Cythere, giving a good definition of its 



* Synopsis of the Characters of the Carboniferous Fossils of Ireland, 

 page 164. 



