PLATE XVII— Continued. 



Productella pyxidata, Hall. 



Fig-. 34. The inteiior of a brachial valve ; showing the cardinal process, muscular scars and brachial ridges. 

 Choteati 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. 



Chemnng 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. T. 



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 c(yunty, N. T. 

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



Chemung group. Coneioango, N. Y. 

 Pig. 46. An enlargement of the surface. 



Genus AULOSTEGES, von Helmersen. 



Page 319. 



Aulosteges Wangenheimi, de Vprneuil. 



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 Davidsok.) 

 Permian. Russia. 



Genus STROPHA.LOSIA, King» 



Page 3U. 



Strophalosia Gerardi, Kiug. 



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

 cicatrix. (After Davidson.) 



Permian. (?) Spiti, India. 



Genus PRODUCTELLA, Hall. 



Page 3-28. 



Productella productoides, Miurhi.son. 



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

 the pedicle- valve. (After Davidson.) 



Upper Devonian. North Devon, England. 



