PLATE LX— Coiitlnued. 



PuGNAX MissouRiENSis, Sluimurd. 

 Figs. 33, 34. Dorsal and profile views of an average example ; isliowing' llie lineate striatioii of the surface. 

 Choteau limestone. Pike county, Missouri. 



LlORHYNCHUS (?) BOONENSIS, SllUlllaid. 

 Fig. 35. Cardinal view of the hinge-plate ; showing its median division and the elevation of the crnra. 



X 3. 



Choteau limestone. Cooper county, Missouri. 



PuGNAX GrEENIANUS, Ullicll. 

 Figs. 36-38. Front, profile and dorsal views of an internal cast of an average individual ; showing the 

 smooth lateral slopes and faint plication of fold and sinus. 

 Keokuk group. New Albany, Indiana. 



Pugnax Uta, Maicoii. 



Figs. 39-41. Dorsal, profile and front views of an average adult .shell. 



Fig. 42. The interior umbonal portion of the brachial valve ; showing the broad hinge-plate and narrow 

 median incision. X 3. 



Coal Measures. Manhattan, Kansas. 



Pugnax explanatus, McCliesiiey. 



Figs. 43-45. Fi'ont, dorsal and protile views, diawn from a sulphur cast of the original specimen. 

 Kaskaskia limestone. Illinois. 



Pugnax, sp. ? 



Figs. 46-48. Protile, front and diir.sal views of an undetermined internal cast. The shell has some points 

 of similarity to the Rhynchonclla IlUnoisensis, Meek and Worthen. 

 Coal Measures. Qraham county, Texas. 



Genu.s HYPOTHYRIS, King. 

 HrpoTHYRrs venustula, Hall (^Riiynchonella cuboides. Sowerin). 



Figs. 49, 50, 52. Cardinal, frontal and jirofile views of a typical specimen ; showing the subcuboidal form, 



low median fold and l)road, deep median sinus. 

 Fig. 51. Front view of an internal cast with fewer plications, and showing the branches of the vascular 



trunks on the sinus. 

 Figs. 63, 54. Internal casts of pedicle-valves ; showing the muscular impression, and some variation in the 



form of the vascular sinuses. 

 Fig. 55. An internal cast of the pedicle-valve, enlarged to show the system of vasculai- sinuses. X 2. 

 Tully limestone. Ovid, N. Y. 



