THE SHELL-LIMESTONE OF DURHAM. 157 



species, I have not ventured to specialise tliem. There was one 

 well-marked individual of triangular contour, which was unfor- 

 tunately lost after it had been outlined, and which, I have little 

 doubt, was the Cytliere acuta of Jones; it was minute and ex- 

 ceedingly globose, and had the ventral margin almost straight, 

 and its dorsal margin convex; its extremities were acute and 

 alike. 



Before closing my remarks on the Permian Entomostraca, I 

 cannot but express how greatly I am indebted to Mr. T. Rupert 

 Jones, for his valuable and ever-ready assistance during my later 

 researches on these fossils. Many of the corrections made in 

 this revise are due to his suggestion. And besides adding notes 

 to the species, from the shell-limestone described by me, he has 

 kindly undertaken to revise his descriptions of those species 

 peculiar to the upper limestone, so that they may be printed 

 along with this paper, and complete the list of Eiitomostraca be- 

 longing to the Permian rocks of Durham. 



ENTOMOSTRACA FROM THE UPPER PERMIAN LIMESTONE OF BYER8 

 QUARRY. BY T. RUPERT JONES, F.G.S. 



In critically examining, at the request of Mr. Kirkby, his col- 

 lection of Eiitomostraca, from the shell-limestone of Tunstall 

 Hill, my attention was necessarily re-drawn to my figures and 

 descriptions of Permian Entomostraca, published in Professor 

 King's " Monograph of the Permian Fossils of England " 

 (Pal^ont. Soc, 1849); and I find some points on which remarks 

 and amendments may be advantageously made, especially as it 

 appears desirable that the species there described should be again 

 briefly noticed in the completion of an account of the Permian 

 Entomostraca of Durham, for the Tyneside Naturalists' Field 

 Club. 



The forms described in the monograph as Dithyrocaris Permi- 

 ana and D. glypta, have already been re-described by Mr. Kirkby 

 and myself as Kirhhya Permiana, in the preceding memoir. 



The generic and sub-generic characters of Cytliere and its sub- 

 groups will be found more especially in my '' Monograph of the 



