PLATE LXXXII— Continued. 



Fig's. 14-16 Dorsal, profile ami ventral views; showing- the plication, contour and piistulose exterior. X B. 

 Fig. 17. The interioi' of a brachial valve ; showing the cardinal ai'ca, wide delthyrimn and well developed 



teeth. X 2. 

 Fig. 18. A view looking into the umlKinal cavity of the ]icdicl('-valvc to .show the elevation of the teeth 



X 3. 

 Fig. 19. Cardinal view of the specimen represented in tigs. 14-lti; .showing the cardinal area on each 



valve, the open delthyrium and cai'dinal pi'ocess. X 3. 

 Fig. 20. The interior of a brachial valve. X 2. 



Fig. 21. An internal cast of tlu> perlicle-vaho ; showing the muscular impressions. X 2. 

 Figs. 22, 23. Interiors of l.)rachial valves ; showing cardinal process and muscular impressions. X 2. 

 Fig. 24. Interior of a brachial valve ; showing the cardinal area and proce.ss, crural plates and muscular 



scars. X 3. 

 Fig. 2,'). An enlargement of the external surface; showing the radiating rows of elongate pustules. 

 Hamilton shales. Prom various Jjealities in Western New York. 



Genus TROPIDOLEPTUS, Hall. 



Page :102. 

 Tropidoleptl's CARINATUS, C'oillild. 



Fig. 26. The pedicle-valve of a very young shell ; showing the acuminate <-ardinal extremities and the 



coarse, simple and sharp plication. X 3. 



Hamilton groujj. Caiiandaigua Lake, New i'ork. 

 Fig. 27. An enlargement of an interior layer of the shell ; showing punctae. 

 Fig. 28. A horizontal section of the shell substance ; showing the radial rows of obliipic ttdiidcs jienetrat- 



ing the fibrous shell substance. 

 Fig. 29. Cardinal view of the umbonal portion of the valves; showing the open delthyrium, the great de- 



velojunenl of the chilidium, and the cardinal area X 3. 

 Figs. 30-32. Ventral, profile and dorsal views of an a\i!rage example ; showing the characters of the ex- 

 terior. 

 Fig. 33 An internal cast of a large pedicle-valve ; showing the impre.ssion of the area, pedicle-cavity, teeth 



and dental ridges. 

 Fig. 34. An internal cast of a brachial ^■alve ; showing the impression of the cai'dinal process and crenu- 



lated dental sockets. 

 Fig. 35. The interior of a pedicle-xiilve ; showing the cardinal area, open delthyrium and the prominent 



crenulated teeth. 

 Fig. 36. The interior of a brachial valve; showing the cai'dinal process, crenulated dental sockets and 



median sejitum. 



Hanulton groiiu. Prma rarioim localities in the argillaceous and arenaceous shales of 

 Central and Western Neio York. 



Tkopidoleptus occidens, Hall. 



Figs. 37, 38. Dorsal and central views of the original specimen of the species. 

 Hamilton grouji. hnra ('itij, Iowa. 



