from the Fossiliferous uimcstone of Durham, 327 



It is dedicated to Dr. Reus3, who has contributed a valuable 

 paper on the Entomostraca of the Permians of Germany. 

 Found rarely in the fossiliferous limestone of Tunstall Hill. 



4. Bairdia Kingii, Reuss. PI. X. figs. 8 & 8 a. 

 B. Kingii, Reuss, Jahresbericht der Wetterau. Gesell. 1851-1853, p. 67. 



Length ~ inch ; height ^ inch. 



Carapace subpentagonal, smooth. Dorsal margin arched. 

 Ventral margin sinuate, becoming rapidly convex at each extre- 

 mity. Anterior and posterior extremities almost alike, subangu- 

 late, the posterior a little less pointed than the anterior. Lateral 

 contour lenticular, slightly concave posteriorly ; greatest diameter 

 one-fourth the length, centrally situate. 



Although I have identified the form just described with B. 

 Kingii, Reuss, there exists a little difference in the general out- 

 line. Reuss' s figure represents the anterior extremity more 

 pointed, and the posterior wider and rounder, than the same 

 features in the Durham form. In other respects they agree ; so 

 that it is perhaps better to consider those slight variations to be 

 of little importance, than to risk creating a synonym. 



B. Kingii was first observed by Dr. Reuss in the Lower Zech- 

 stein of Bleichenbach. It is a rare species in the fossiliferous 

 limestone of Tunstall Hill. 



5. Bairdia mucronata, Reuss. PI. X. figs. 9, 10, & 11 ? 

 B. mucronata, Reuss, Jahresbericht der Wetterau. Gesell. 1851-53, p. 67. 



Length ^ i ncn ; height ^j inch. 



Carapace subcuneiform, smooth, ventricose centrally, com- 

 pressed towards extremities. Dorsal margin convex centrally ; 

 anterior slope slight, only one-fourth of height, somewhat con- 

 cave, joining the ventral margin almost at a right angle ; poste- 

 rior slope deeply sinuate, falling three-fourths of height, more 

 or less abruptly. Ventral margin almost straight, or slightly 

 sinuate. Anterior extremity wide, subangular, sometimes angu- 

 lar. Posterior extremity acutely rostrated, very much produced, 

 and occasionally curved upwards. Lateral contour nearly lenti- 

 cular, slightly concave at each extremity ; greatest diameter rather 

 more than one-fourth of length, centrally situate. Flange of 

 left ventral margin long, but narrow, posteriorly situate. Hinge 

 with left dorsal margin rather largely overlapping the right. 



This fine species is subject to modifications of outline. Figs. 

 9, 10, and 11 ? represent the most common forms. Its sharp, 

 produced posterior extremity, which is the characteristic fea- 

 ture of the species, varies in length ; fig. 10 gives the most pro- 

 duced form. Some individuals have the anterior extremity 



