PI,ATK XLVII— Coutinuert. 



Seminula subtilita, Hall. 



A view of the hinge-plate ; showing its excavate upper face, subqnadrate outline, striated pos- 

 terior exten.sions and minute visceral foramen. X 5. 

 (?) Chester limestone. Caldwell county, Kentucky. 

 The hinge-plate of another specimen ; showing some differences in outline and surface. The 

 position of the visceral foramen is occupied by a minute lobe. X 5. 

 Coal Measures. Maiiliattan, Kansas. 

 A dor.«ial view of an orbicular and faintly lobed form. 

 Coal Measui'es. Coppers Creek, Iowa. 



A large siiecimen, very broad in the pallial region and strongly lobed on the anterior margin. 

 (?) Chester limestone. Chester, Illinois. 



A lai'ge individual with greatest width more posterior, strong anterior lobe, and shai-p concentric 

 lines. 



Coal Measui'es. Chariton county, Missouri. 

 An extremely trilobed shell with the greatest width near the anterior margin. The fine radiating 

 lines upon the shell are seen only where the epidermal layer has been abraded. 

 Coal Measures. Winterset, Iowa. 

 An extremely elongate form, broadly lobed on the anterior margin. 



Coal Measures. Miami county, Kansas. 

 The interior of the pedicle-valve of an old and much thickened shell ; showing the deep pedicle- 

 cavity and the broad, obscnrely-detined muscular ai'ea. 

 Coal Measures. Katisas City, Missouri. 

 An internal cast of the spiral cones, viewed from the dorsal side. 



Coal Measures. Locality f 

 A preparation of the brachidium, a portion of the spirals being cut away to expose the loop. The 

 figure shows the fui-cated anterior extremity of the saddle, the position and extent of the 

 accessory lamellae and the fimbriation of the antei-ior portion of the fir-st few lamellie of the 

 coils. X 3. (c.) 



Coal Measures. Winterset, Iowa. 

 Fig. 27. A dorsal view of an internal cast slightly restored at the beak ; showing the adductor scars and 



vascular impressions. 

 Fig. 28. The opposite side of the same specimen ; showing the adductor scars while the diductors are 

 not clearly defined. This is a cast in iron-stone and its source is undetermined, but it is prob- 

 ably from the 



Coal Measures. Ohio. 

 Fig. 29. The interior of a vei'y elongate and much thickened pedicle-valve ; showing the adductor and 

 diductor scars deeply excavated in the shell substance. X 2. 

 Coal Measures. Near Kansas City, Missouri. 

 Fig. 30. Anterior marginal view of a large and old shell with greatly thickened valves. This shell is of 

 the form represented in figure 22, but is much older and is somewhat unsymmetrical, having 

 suffered injury at the right of the median fold. 

 Fig. 31. A preparation of the brachidium, the upper half of the spiral cones having been removed. This 

 figure has been drawn from a transparency, and the saddle of the loop appears very long. 

 Through an eri'or in lithography the lateral liranches of the loop have been disconnected from 

 the primary lamellae. X 2. (c.) 



Coal Measures. Winterset, Iowa. 



Seminitla Dawsoni, sp. uov. (= Athyrls SUBTILITA, Davidsou). 



Fig. 32. A view of the brarhidium naturally preserved by incrustation and exposed by the removal of a 

 portion of the pedicle-valve ; showing the form of the cones and the position of the accessory 

 lamelljE. X 2. 



Fig. 33. A dorsal view of the exterior of conjoined valves. X 2. 



Fig. 34. A profile view of the same specimen. X 2. 



Coal Measures. Windsor, Nova Scotia. 



Athyris (Seminula ?) sp. ? 



Fig. 35. A transparency viewed from the ventral side ; showing the attachment of the crura to the primary 

 lamellie, a portion of the loop and the accessory lamelte and the fimbriated coils of the spirals. 

 The specimen is interesting in showing the asymmetry of the coils, the cone on the left side 

 possessing eleven volutions, that on the right but eight. The tilling of the shell is transparent 

 calcite and the brachidium has been replaced by red hematite. X 3. (c.) 

 Coal Measures ? Ohio. 



