PLATE XVII—Continued. 
Productella pyxidata, Hall. 
Fig. 34. The interior of a brachial valve ; showing the cardinal process, muscular scars and brachial ridges. 
Choteau 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 posterior face. 
Chemung group. Cattaraugus county, N. Y. 
Productella hirsuta, var. rectispina, Hall. 
Fig. 37. The interior of a brachial valve; showing the cardinal process and slightly developed crural plates. 
Chemung group. Steuben county, N. Y. 
Productella 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 Verneuil. 
Figs. 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 STROPHALOSIA, 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 PRODUCTELLA, Hall. 
Page 328. 
Productella 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. North Devon, England. 
