PLATE XVn— Continued. 



Produotella pyxidata, Hall. 



Fig-. 34. The interior of a brachial valve ; showing- the cardinal process, muscular scare and brachial ridg-es. 

 Choteaii limestone. Pike county, Missouri. 



Productella arctirostrata, Hall. 



Fig. 36. The impression of the exterior of a brachial valve ; showing that the cardinal process is quadrilo- 

 bate on its poateiior face. 



Chemung- group. Cattaraugus county, N. Y. 



Produotella hirsuta, var. rectispina, Hall. 



Fig. 37. The interioi- of a brachial valve ; showing- the cardinal process and slightly developed ci-ural plates. 

 Chemung group. Steuben county, iV. F. 



Produotella onusta, Hall. 



Fig. 40. The interior of a brachial valve ; showing cardinal process, dental sockets, muscular and brachial 



impressions. 

 Fig. 41. An exfoliated exterior of the pedicle-valve. 



Chemung group. Cattaraugus county, N. Y. 

 Figs. 42, 43. Cardinal views of internal casts of the pedicle-valve ; showing the muscular scars. 



Chemung group. Conewango, N. Y. 

 Fig. 46. An enlargement of the surface. 



Genus AULOSTEGES, von Helmersen. 



Page 319. 



Aulosteges Wangenheimi, de Vprueuil. 



Pigs. 47, 48. Two views of a specimen ; showing the highly developed cardinal area and deltidium. 

 Fig. 49. The interior of a brachial valve. (After Davidson.) 

 Permian. Russia. 



Genus STROPHA.LOSIA, King. 



Page 314. 



Strophalosia Gerardi, King. 



Fig. 50. View of the shell ; showing the lamellose brachial valve, cardinal areas, deltidia and the umbonal 

 cicatrix. (After Davidson.) 



Permian. (?) Spiti, India. 



Genus PEODUCTELLA, Hall. 



Page 328. 



Produotella productoides, Murchison. 



Fig. 51. View from the brachial valve ; showing the cardinal area and deltidia, and the marginal spines of 

 the pedicle- valve. (After Davidson.) 



Upper Devonian. Nwth Devon, England. 



