PLATE LVII—Continued. 
CaMAROT(ECHIA (?) DUPLICATA, Hal]. 
Figs. 36-38. Ventral, frontal and dorsal views of the original example ; showing the single plication and 
sulcus on sinus and fold respectively, and the obscure and sparse lateral plication. 
Fig. 39. The interior of a brachial valve, drawn from a gutta-percha cast; showing the hinge-plate, crura, 
median septum and muscular impressions, and also the thickening of the shell in the umbonal 
region. X 2. 
Chemung group. Cattaraugus county, N. F. 
Camarot®chia Dotis, Hall. 
Figs. 40, 41. Ventral and profile views of a specimen of i-ather broad form, with rounded plications. 
Hamilton group. Eighteen-Mile Creek, N. Y. 
Camarotcechia prolifica, Hall. 
Figs. 42, 43. Dorsal views of two internal casts ; showing slight differences in the degree of its plication. 
Hamilton grouji. Schoharie and Otsego counties, N. Y. 
Camarot®citia eximia, Hall. 
Figs. 44, 4r). Cardinal and dorsal views of an internal cast. 
Chemung group. Ithaca, N. Y. 
Camarotoechia orbicularis, Hall. 
E'ig. 46. An internal cast of a brachial valve ; showing the cast of the spondylium. 
Fig. 47. Cardinal view of an internal cast; showing the filling of the rostral cavity and the extent of the 
thickened median septum. 
Fig. 48. An internal cast of the pedicle-valve ; showing the adductor and diductor muscles and the ovarian 
markings. 
Fig. 50. An enlargement of a portion of the interior of the pedicle-valve; showing the detailed structure 
of the muscular impression. 
Chemung group. Meadville, Pennsylvania. 
Camarotcechia contracta, Hall. 
Fig. 49. An internal cast of the pedicle-valve ; showing the form of the muscular area. (See figs. 28-32.) 
Hamilton group. Near Cardiff, N. Y. 
Camarotcechia, s)). ? 
Figs. 51-53. Ventral, profile and dorsal views of an internal cast in chert. 
Burlington limestone. Burlingtmi, Iowa. 
Camarotcechia, sp. indet. 
Fig. 54. Cardinal view of an extremely gibbous internal cast; showing the filling of the muscular cavity 
in the pedicle-valve and the spondylium in the brachial valve, the cavities left by the dental 
plates, hinge-plate, crura and median septum. 
Waverly gi-oup. Ohio. 
