Palaeozoic Bivalved Entomostraca. 29 



illustrative of the species described by Count Miinster in 

 1830 *. 



In July 1866, in another paper f, we discussed what 

 had been done by British authors, from the time of Ure 

 (1793) to that of M'Coy (1844), our observations being- 

 based, in several instances, on an examination of type spe- 

 cimens. 



In 1867 we gave, in the ' Transactions of the Geological 

 Society of Glasgow,' a list and short account of the Ento- 

 mostraca occurring in the Carboniferous rocks of Scotland J. 

 The list included a great many new species (discovered by 

 Mr. John Young and other Members of the above Society), 

 most of which have yet to be described and figured. 



In 1870 one of us described some species (Carbonice &c.) 

 from South Wales §. 



Lastly, in 1875 1|, we noticed some Russian specimens 

 presented to us by the late M. d'Eichwald, with a few from 

 the late Sir R. I. Murchison's collection. 



These papers, though slight, have helped to clear the way 

 for the description of new species, by showing what others 

 have done in this field of research, and what our opinion was 

 of the results of their work, with a view to the rectification 

 and unification of the synonymy, and to the determination of 

 numerous species not yet described. 



Among other materials which have accumulated in our 

 many years' study of Carboniferous Entomostraca is a large 

 suite of specimens belonging to a group of seven species, 

 hitherto referred to Cythere, but which apparently belong to 

 the genus Carbonia, established by one of us, in 1870, for 

 the reception of two species from the Coal-measures of South 

 Wales. It is proposed to give a brief account of the seven 

 species in the present paper. 



The species in question have the form of ordinary Cytherce, 

 but differ from them in possessing a circular muscle-spot near 

 the centre of each valve, after the manner of Leperditia. 

 The muscle-spot is commonly seen in casts as a slightly 

 raised tubercle. When the interior, of the carapace-valves is 

 exposed (which is not often), the spot appears as a shallow 

 excavation. In some of the ironstones of the west of Scot- 



* Leonhard und Bronn's ' Jahrbuch fiir Mineralogie ' «!cc. Jahrg. 1830, 

 pp. 60-70. 



t Ann. & Mag. Nat. Hist. ser. 3, vol. xviii. p. 32. 

 \ Trans. Geol. Soc. Glasgow, vol. ii. p. 213. 

 § Geol. Mag. vol. vii. p. 214. 

 || Ann. & Mag. Nat. Hist. ser. 4, vol. xv. p. 52. 



