PLATE LXXXI— Continued. 



Fijj. 31. Dorsal view of an internal cast of a narrow and elongate shell, in which tho impression of the 



muscular platform of the brachial valve is sharply defined. 

 Fig. H2. A gutta-percha impression made from the same specimen ; showing the collar or inverted lamella 

 alKuit the foramen, a portiiin of the dental plates and the form of the muscular platform. 

 Upper Carbcmiferous limi'stone. iSontfiem Indiana. 

 Figs. 33-3.5. Profile, dorsal and venti'al views of a large and characteristic example ; showing the curvature 

 of the valves, the bi'oad concavity of the pedicle-valve and the reflexion of the anterior mar- 

 gins ; also the oblique foraminal aperture. 



Upper Carboniferous lime.stone. HarHson nmnty, Missouri. 



DiELASMA. .sp. ? 



Fig. 36. Cardinul view of a specimen enlarged to show the obliijue opening of the jiedicle-passage and its 



cross-striated surface. X 3. 

 Fig. 37. An internal cast of the brachial \al\e ; showing the form and striation of the muscular platfoi-m. 



X3. 



Chester gi-oup. Caldwell county, Kentucky. 



DiELASMA OBOVATA, Sp. UOV. 



Figs. 38-40. Doraal, profile and ventral views of a specimen having the aspect of D. fnrmosa, liut said to he 

 from the Coal Measures. 



Coal Measures. Kentucky. 



Genus CRYPTONELLA, Hall. 



Page 281;. 



Cryptonella subelliptica. s]). nov. 



Figs. 41-43. Dorsal, profile and ventral riews of a large internal i'a.st in iron-stone ; showing the form, con- 

 tour and muscular .scars of the brachial valve. 

 Waverly group, ifs'ciotomlle, OMo. 



