Palceozoic Bivalved Entomostraca. 187 



the curvatures and connections of the riblets. Surface not re- 

 ticulated so far as known. Length ^"sV inch. 



The above description is taken from specimens which we 

 identify with Prof. M'Coy's Cythere costata, but which do not 

 exactly agree with the figures of the species in his ' Synopsis 

 of the Characters of the Carboniferous Fossils of Ireland.' In 

 all probability his specimens may not have been so perfect as 

 ours ; or the latter may possibly differ somewhat from the 

 Irish examples. However this may be we think it well to 

 assume that the highly costated species now described is the 

 same as M'Coy's. 



Localities. — England. Carboniferous-Limestone series : 

 Steeraway, Salop ; Weston-super-Mare, Somerset ; Railway- 

 cutting near Heversham, Westmoreland ; Cam Beck, Cum- 

 berland ; Plashetts, Northumberland. 



Scotland. Carboniferous Limestone (Lower) : Brockley, 

 Lanarkshire ; Cults Lime-works, Fifeshire. 



8a. Var. Mooreana. (PL III. fig. 15.) 

 From Weston-super-Mare we have seen another costated 

 Kirkbya, rather resembling the present species, but relatively 

 much shorter and more subquadrate in outline, the height 

 being two thirds of the length. The costation likewise is 

 slightly different ; and the subcentral pit takes more the form 

 of a transverse slit. This may possibly be a distinct species ; 

 for the present we term it K. costata, var. Mooreana. It was 

 collected by the late Mr. Charles Moore, of Balh. 



9. Kirhbya scotica, Jones & Kirkby. 

 (PI. III. figs. 16 & 17.) 



Kirkbi/a scotica, J. & K., 1807, Trans. Geol. Soc. Glasgow, vol. ii. 



p. 220 ; 1871, vol. iii. Suppl. p. 28. 

 Kirkhya scotica, Armstrong and others, 1870, Catal. W.-Scot. Foss. 



p. 45. 



Subrhomboidal, compressed, uniformly highest in the 

 central third ; height more than half the length. Dorsal 

 border straight and over two thirds of the maximum length ; 

 ventral border slightly convex ; extremities obliquely rounded, 

 the posterior having the longest curve above, and the anterior 

 below. Lateral contour (edge view) compressed-oblong. 

 Subcentral pit roundish oval, and nearly in the centre of the 

 valve in most cases. Valves covered with numerous (twelve 

 or more) sinuous and inosculating ribs, somewhat concen- 

 tric lengthwise and obliquely arranged. The ribs become less 

 concentric and more parallel in some cases, as in fig. 17. 

 Surface otherwise smooth, so far as known. Length -^ inch. 

 This species, which was discovered by Mr. James Thomson, 



