PLATK LXXXIV— Continued. 



Strophonklla costatula, s[). nov. 



Figs. 15, Ifi. Dorsal and profile views of the shell ; showing the revei-sed convexity of the valves and the 

 shai-ply rounded, irregularly dichotomizing- plications. 

 Niagara group. Loawville, Kentucky. 



Rafinesquina alteunata. Conrad. 



Figs. 17, 18. Enlargements of umbonal portions of internal casts of the pedicle-valve, to show the filling of 

 the pedicle-passage. In fig. 18, which repi'esents the older shell, this filling is seen to be the 

 smaller and is consti-icted at its hase, evincing thus the tendency of the shell to close this pas- 

 sage at its inner extremity. X 3. 



Hudson River group. Erratic blocks hi western iVeio York. 



Productella navicella, Hall, 



See Plate 17. 

 Fig. 19. A small pedicle-valve preserving the spines in a perfect condition and showing the convergence 

 of the cardinal spines. X 5. 



Hamilton group. CanandaigvM Lake, Next) York. 



Strophalosia Rockfordensis, sp. nov. 



See Plate 17a. 

 Figs. 20, 21, 22. Ventral, dorsal and cardinal views of a specimen ; showing the general extei-nal characters 

 and the umbonal cicatrix 



Upper Devonian. Rockford, loxea.. 



Plectambonites producta, sp. nov. 



Figs. 23, 24, 25. Cardinal, profile and front views of an internal cast of a pedicle-valve ; showing the form 

 of the teeth and muscular impressions, the short hinge and the greatly produced anterior 

 margin. 



Niagara dolomites. Yellow Sprinffs, Ohio. 



Hyattei.la congesta, Hall. 



See Plate 40. 

 Figs 26-28. Doi-sal, front and j)rofile views of one of the oi'iginal si)ecimens (Palaeontology of New York, 

 vol. II. pi. xxiii, figs. 1, f, g, i). 



Clinton group, ilouroe coiiiity. New York. 



SriKiFEU L^vis, Hall. 

 See Plate 38. 

 Fig. 29. A portion of the cardinal region enlarged to show the peculiar structure of the deltarium, which 

 beare a (nrcular jjerforation with elevateii margins, and is surrounded by an elongate, smooth 

 area, at the edges of which the growth lines are sharply interrupted. X 3. 

 Chemung group. Near Ithaca, New York. 



Seminula subquadrata, Hall. 



See Plate 47. 

 Figs. 30, 31. Dorsal and profile views of the original specimen. 

 Kaskasia limestone. Chester, Illiiwig. 



Cliothyris Royssii, L6veille. 

 Fig. 32. The interior of a brachial valve ; showing the form of the hinge-plate. 

 Coal Measures. Toumai, Belgium. 



Athyris conoentrica, voh Biicli. 



Fig. 33. An enlargement of the hinge-jilate ; showing its form, tripartite division, and apical perforation. 

 Middle Devonian. Ferqiies, Brittany. 



