178 Messrs. Jones and Kirkby on the 



Ceratiocaris ? permiana, Jones, in Morris's Catal. Brit. Foss. 1854, 



p. 103. 

 Leperditia ? permiana, Kirkby, 1858, Ann. & JNIag. Nat. Hist. ser. 3, 



vol. ii. p. 434, pi. xi. figs. 5-13. 

 Kirkbya permiana, Jones & Kirkby, 1859, Trans. Tyneside Field-Club, 



vol. iv. p. 129, pi. viii. a. figs. 1, 2, 3, and 5 (figs. 4 and 7, K. glypta), 



pi. x. figs. 5, 7, 9-12 ( figs. 6 and 8 K glypta). 

 Kirkbya permiana, Kirkby, 1861, Quart. Journ. Geol. Soc. vol. xvn. 



p. 308. 

 Kirkbya permiana, Jones & Kirkby, 18G7, Trans. Geol. Soc. Glasgow, 



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

 Kirkbya permiana, Armstrong and others, 1876, Catal. Western- 

 Scottish Foss. p. 44. 

 Kirkbya permiana, J. & K. 1880, Quart. Journ. Geol. Soc. vol. xxxvi. 



p. 588. 



This species, as a Permian " recurrent," was fully described 

 in the ' Annals and Magazine of Natural History ' for Nov. 

 1858; and again, in more detail, in the ' Transactions of the 

 Tyneside Field-Club' for 1859. The descriptions and 

 figures there given of Permian specimens from the Mag- 

 nesian Limestone of Tunstall Hill would do equally well 

 for most of the many Carboniferous examples of the species 

 that have come under our notice ; but, for convenience, we 

 describe it from the latter as follows : — 



Carapace ark-shaped or suboblong, flatly convex or com- 

 pressed, height half the length or rather more. Dorsal 

 border straight, sometimes the full length of the valve, some- 

 times rather less, according to the relative boldness of the 

 curve of the extremities ; ventral border faintly incurved, 

 straight, or gently convex in its middle third, and boldly 

 curved at the extremities, the anterior extremity being the 

 most acute. The extremities and ventral portion of each 

 valve are bordered by two parallel, concentric rims or expan- 

 sions, which project a considerable distance beyond the sur- 

 face of the valve. A small oval pit occupies a subcentral 

 position on each valve, and the surface is beautifully reticu- 

 lated. Length ^ inch. 



The Carboniferous specimens of this species vary consider- 

 ably in character. The drawing here given (PI. III. fig. 1) 

 is that of an average good specimen ; other illustrative figures 

 would have been given had circumstances allowed. 



The outline of the valves is usually as described above ; 

 but sometimes the extremities and ventral margin almost 

 approximate the curve of a semicircle in the regularity of 

 their contour ; from this extreme the ends by degrees become 

 more abruptly sloped, and the ventral border straightened, 

 until an oblong figure is approached. 



Many examples have the valves much depressed, others 

 have them moderately convex (and so form a carapace of fair 



