PLATK XLVII— Coulliiued. 



Seminula subtilita, Hall. 



Vig. 17. A view of the hing-u-plate ; showing: its excavate upper face, subquadrate outline, striated pos- 

 terior extensions and minute visceral foramen. X 6. 

 (t) Chester limestone. Caldwell county, Kentucky. 



Fig. 18. The hinge-plate of another specimen ; showing some differences in outline and surface. The 

 position of the visceral foramen ia occupied by a minute lobe. X 6. 



Coal Measures. Manhattan, Kansas. 

 Vig. 19. A dorsal view of an orbicular and faintly lobed form. 



Coal Measures. Coppers Creek, Iowa. 



Vig. 90. A large specimen, very bread in the |)allial region and strongly lobed on the anterior margin. 



(f) Chester limestone. Che.<<ter, Illinois. 

 Fig. 21. A large individual with greatest width more posterior, Strang anterior lobe, and sharp concentric 

 lines. 



Coal Measures. Chariton county, Missouri. 

 Pig. 33. An extremely trilobed shell with the greatest width near the anterior margin. The fine radiating 

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

 Coal Measures. Winterset, Iowa. 

 Fig. 23. An extremely elongate form, broadly lobed on the anterior margin. 



Coal Measures. Miami county, Kansas. 

 Fig. 24. The interior of the pedicle-valve of an old and much thickened shell ; showing the deep pedicle- 

 cavity and the broad, obscurely-defined muscular area. 

 Coal Measures. Kansas City, Missouri. 

 Fig. 36. An internal cast of the spiral cones, viewed from the dorsal side. 



Coal Measures. Locality f 

 Fig. 26. A preparation of the brachidium, a portion of the spirals being cut away to expose the loop. The 

 figure shows the furcated anterior extremity of the saddle, the position and extent of the 

 accessory lamellse and the fimbriation of the anterior portion of the first few lamellte of the 

 coils. X 3. (c.) 



Coal Measures. Winterset, Imoa. 

 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 pi-ob- 

 ably from the 



Coal Measures. Ohio. 

 Fig. 29. The interior of a very 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, Miisouri. 

 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 brachi<lium, 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 error in lithography the lateral branches of the loop have been disconnected from 

 the primary lamellae. X 2. (o.) 



Coal Measures. Winterset, Iowa. 



Semintila Dawsoni, sp. nov. (= Athtkis scbtilita, Davidson). 



Vig. 82. A view of the brai-hidium 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 

 lamells. X 2. 



Pig. 83. A dorsal view of the exterior of conjoined valves. X 2. 



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



Coal Measures. Wimlsor, Nom Scotia. 



Athykis (Seminula ?) sp. 



Kg. 36. A transparency viewed from the ventral side j showing the attachment of the crura to the primary 

 lamella;, a portion of the loop and the accessory lamellae and the fimbriated coils of the spirals. 

 The sjjecinien 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 filling of the shell is transparent 

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

 Cokl Measures ) Ohio. 



