ANIMALS. 61 



calcareous Grit, and imbedded in the crystalline Limestone. They also occur, but much 

 more sparingly, in the Limestone of Humbleton, and other localities. Species Nos. 

 1 and 3 occur exclusively in the latter rock ; No. 2 occurs in both rocks ; and the 

 others, except No. 4, have as yet been found in the Limestone from Byers' Quarry only. 



No. 1. Cythere Morrisiana, nobis. Tab. XVIII, fig. 2 a, b, c. 



INCH. 



Length, -^^ 

 Height, Jq 

 Thickness, ^V 



Carapace irregular oblong, convex, smooth. Dorsal and ventral borders nearly 

 straight, slightly incurved. Extremities subacute, suddenly depressed ; the anterior 

 slightly narrower than the posterior. 



Dorsal aspect elongate oval, compressed at the ends ; anterior sub-ovate. 



Unique. Locality, Humbleton. 



This well-marked species is named after Mr. J. Morris, to whose scientific 

 researches palaeontologists are so greatly indebted. 



No. 2. Cythere (Bairdia) curt a, M'Co^. Tab. XVII, figs. 21, 22 ; and Tab. XVIII, 

 fig. 3 a, b, c. 



Baiedia curtus, M'Coy, 1844. Syn. Char., &c., p. 165, pi. xxiii, fig. 6. 



INCH. INCH. 



Length, -^ 



■h 



Height, ^V 



1 



ITS 



Thickness, -Jj- 



rh 



Carapace suh-tnaiigvlsiT, convex, smooth. Dorsal border -proiecting ; ventral sinuous. 

 Anterior extremity rounded on its ventral half, and forming an angle with the sloping 

 dorsal border ; posterior acute. 



Dorsal aspect narrow acute oval ; anterior compressed ovate. 



Several specimens exhibit, more or less distinctly, the interior of the valves, which 

 closely resemble those of B. subdeltoidea, Miinster,^ of the Chalk and Tertiary for- 

 mations. The cast (figs. 21, 22), in particular, is similar to the cretaceous species, and 

 not very dissimilar to B. affinis, Morris,^ but the generality of the Permian specimens 

 are narrower, more compressed, and less triangular than the species referred to. 



Found by Mr. Grifi&th in the Carboniferous rocks of Ireland. 



Not uncommon at Byers' Quarry and Humbleton. 



1 See Jones, Mon. Entom. Cret. Form., p. 23, tab. v. fig. 15. 



2 Phys. Descript. New S. Wales, &c., p. 291, pi. xviii, fig. 10. 



