30 Prof. T. R. Jones and Mr. J. W. Kirkby on 



land, where the valves are of a bright black colour, the spot 

 is white. 



These Carbonice are from: — (1) the Calciferous Sandstone 

 or Lower Carboniferous series of Scotland ; (2) the coal- 

 bearing strata of the Carboniferous Limestone series of the 

 same country ; and (3) the Coal-measures of England, 

 Wales, and Scotland. They occur in bituminous shales, in 

 blackband and clay band ironstones, in parrot-coals, and in 

 impure limestones. Individuals of some of the species, more 

 particularly of C. fabulina, appear to have swarmed in the 

 waters in which these deposits were formed. Some of the 

 strata arc literally full of their remains. They are essen- 

 tially characteristic of the carbonaceous portions of the Car- 

 boniferous System. Wherever conditions suitable for the 

 laying down of Coal-measures prevailed, there these Ento- 

 mostraca flourished, almost to the exclusion of species of other 

 genera. 



It ought to be mentioned that we are greatly indebted, for 

 multitudes of specimens from the west of Scotland, and for 

 much information as to the distribution of the species, to Mr. 

 John Young, of Glasgow, who is also the discoverer of 

 several of the species here described. For other specimens 

 we have to thank Mr. James Armstrong and Mr. James 

 Thomson of Glasgow, Dr. Rankine of Carluke, Mr. Grossart 

 of Shotts, Mr. E. W. Binney of Manchester, Mr. John Ward 

 of Longton, and other friends. Our examination of the very 

 numerous specimens collected by the Geological Surveyors 

 of Scotland has greatly enlarged our knowledge of this 

 genus. 



Genus Carbonia, Jones (1870). 



Valves (as known) subovate, ovate-oblong, or elongate ; 

 anterior third usually smaller than the posterior ; the right 

 valve slightly larger than the left, overlapping it some- 

 times along the middle portion of the ventral edge. Hinge- 

 line in the middle third of dorsal margin, more or less defined 

 between the anterior and posterior curved slopes of the dorsal 

 margin. Hinge simple. Muscle-spot circular, enclosing 

 three or four translucent spots or a lobed pattern ; level or 

 slightly depressed on the outside, somewhat hollow within. 

 The valves are bent inwards, in some cases, near the muscle- 

 spots, and leave slight, subcentral, transverse furrows on the 

 cast. 



The round and spotted muscle-mark, hollow within, is 

 characteristic of this genus. 



