158 Annals of the Carnegie Museum. 



Plate XXVII. 



1. Chonetes graniilifer Owen. Six specimens from the Ames limestone at the 

 Brilliant cut-off, Pittsburgh, Pa. Approximately natural size. 



2. Pelalodus okioensis Safford. A specimen from the Ames limestone at City 

 Farm, opposite Homestead, Pa. Approximately natural size. 



3. Pugnax Utah (Marcou). Three specimens from the Ames limestone at the 

 Brilliant cut-off, Pittsburgh, Pa. Approximately natural size. 



4. Lophophyllnm profundiim Milne-Edwards and Haime. Two specimens 

 from the Ames limestone at the Brilliant cut-off, Pittsburgh, Pa. Approximately 

 natural size. 



5. 6. Allorisma suhcuneatum Meek and Hayden. Two specimens from the 

 Birmingham shale below Kennywood Park, near Duquesne, Pa. Approximately 

 natural size. 



7. Tainoceras occiclenlale (Swallow). View of the venter of a specimen from 

 the Ames limestone at Pitcairn, Pa. Approximately natural size. Collected by 

 the Rev. P. E. Nordgren. 



8. Derby a robusta (Hall). A specimen from the Ames limestone at Glenwood, 

 Pa. Approximately natural size. 



Plate XXVIII. 



1. Composila girtyi Raymond. Three views of a wide individual with a shallow 

 sinus and nearly equal valves. All of figures i-ii are one-half larger than natural 

 size, and are all from specimens collected from the Vanport limestone at New Castle, 

 Pa. 



2. The same species. A specimen similar to the preceding, but with a deeper 

 sinus. 



3. The same species. A narrow individual with a deep pedicle valve. 



4. The same species. A narrow shell with almost no sinus. 



5. The same species. A small specimen with a slight sinus in both valves. 



6. The same species. A narrow individual with a very convex pedicle valve. 



7. The same species. A wide specimen with subcircular outline and shallow 

 sinus. 



8. The same species. A narrow shell with pentagonal outline and convex 

 valves. 



9. The same species. Four views of a somewhat square shell with nearly equal 

 valves and a slight sinus. 



10. The same species. A narrow shell with an extermely convex pedicle valve. 



11. The same species. Four views of a wide shell with a pronounced sinus and 

 nearly equal valves. 



12. Orbiculoidea planodisca Raymond. A dorsal valve from the Birmingham 

 shale at Summerhill, Pa. Natural size. 



13. The same species. A pedicle valve from the same locality. Natural size. 



14. Glaphurochilon simplex Raymond. A tail- valve (holotype), from the Van- 

 port limestone at New Castle, Pa. Twice natural size. 



15. 16. Glaphurochilon carbonarius (Stevens). Copies of Meek and Worthen's 

 figures of the tail-valve to illustrate the characters of the genus and to compare 

 with the figure of G. simplex. 



