PLATE LXXXII-Contlnued. 



Figa. 14-16 Donial, profile and ventral \-iews ; showing' the plication, contour and pustuloae exterior. X 3. 

 Fig. 17. The interior of a brachial valve; showing the canlinal area, wide delthyrium and well developed 



teeth. X 2. 

 Vig. 18. A ^-iew looking into the umbonal cavity of the pedicle-valve to show the elevation of the teeth 



X3. 

 Fig. 19. Cardinal Wew of the specimen representeil in tigs. 14-16; showing the cardinal area on each 



valve, the open delthjriiini and cai-dinal pi-ocess. X 3. 

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



Fig. 21. An internal cast of the pedicle-valve ; showing the muscular impressions. X 2. 

 Rgs. 22, 23. Interiors of brachial valves ; showing cardinal ])roce88 and muscular impres.sion8. X 2. 

 Fig. 24. Interior of a brachial valve; showing the car<linal iii-ea and process, crural plates and muscular 



scars. X 3. 

 Kg. 25. An enlargement of the external surface ; showing the radiating rows of elongate pustules. 

 Hamilton shales. From various loealitUs in Western New York. 



Genus TROPIDOLEPTUS, Hall. 



I'Mge a02. 



Tropidoleptus CARINATU8, Couiad. 



Rg. 26. The pedicle-valve of a very young shell ; showing the acuminate cai-dinal extremities and the 

 coarse, simple and sharp plication. X 3. 



Hamilton group. Caaaiidaigita Lake, New York. 



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



Fig. 28. A horizontal section of the shell .substance ; showing the radial rows tif obli<jue tubules penetrat- 

 ing the fibrous shell .substance. 



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

 velopment of the chilidium, an<l the cai"dinal ai-ea. X 3. 



Figs. 30-32. Ventral, profile and doi-sal views of an avei-age example ; t-howing the charactei-s of the ex- 

 terior. 



Kg. 33 An internal cast of a large pedicle-valve ; showing the impression of the area, pedicle-cavity, teeth 

 and dental ridges. 



Pig. 34. An internal cast of a brachial valve; showing the impression of the cardinal process and crenu- 

 lated dental sockets. 



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

 crenulated teeth. 



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

 median septum. 



Hamilton group. l<\om various localities in tlte argillaceous and arenaeeoiui s?wJes of 

 Central and Western New York. 



Tropidoleptus occidens, Hull. 



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

 Hamilton gi-oup. Iowa City, Iowa. 



