THE SHELL-LIMESTONE OF DURHAJf. 133 



posing Dr. Scouler's species belong to the same group, which may- 

 be taken for granted until proved to the contrary. 



All the examples of A". Permiana which came under the notice 

 of Mr. Jones were, as stated before, more or less imperfect, so it 

 may naturally be supposed that great difficulty would occur in 

 attempting to determine the generic affinities of the species to 

 which they belonged. It was evidently owing to this cause 

 that Mr. Jones supposed that it might be a member of Dithjro- 

 caris. It is from the perfect state of preservation of my speci- 

 mens that I have been enabled to offer the preceding remarks 

 in addition to those of Mr. Jones. And as some of the specimens 

 have their valves united and in close juxtaposition, I have also 

 been enabled to prove that the species is a bivalve Entomos- 

 tracan^ like Cijthere^ or rather Beyrichia, consequently that it has 

 no affinity to Dithyrocaris^ or to Ceratiocaris, to which Mr. Jones 

 afterwards referred it, the closely fitting edges of its carapace, of 

 course, excluding it from that genus. 



German and Russian palaeontologists have referred congeneric 

 forms to Cythere; but, with the exception of being bivalve, they 

 possess no characters to warrant their remaining in that genus. 



REMAm\:S BY T. RUPERT JONES, F.G.S. 



The specimens of Magnesian limestone with which Professor 

 King supplied me in 1849, for the obtaining of i^ora^^mwyj^r^ and 

 Eritomostraca, to be described in the " Monograph of the Per- 

 mian Fossils of England," yielded numerous casts and indifferently 

 preserved valves of Entomostraca^ which I could not place with 

 the Cytheres, on account of their relative size, shape, and style 

 of ornament, and which I erroneously referred to Dithyrocaris 

 (seeing some apparent relation between them and D. tenuistriatus). 

 Subsequently I suggested to Mr. Morris, when he was joreparing 

 the new edition of his " Catalogue," that these Permian Ento- 

 mostraca should be removed from Dithyrocaris, and provisionally 

 placed with the bivalvular Ceratiocaris, until we should know 

 more about them. At this time Professor Reuss figured and 

 described an evidently allied form, under the name of Cythere 

 Roessleri, from the Lower Zechstein of Bleichenlmch ; and soon 



