C. E. Beecher — N. A. Species of Strophalosia. 245 



Geological position. — In the Keokuk shales at Crawfords- 

 ville, Indiana. Collected by Professor F. H. Bradley and Rev. 

 D. A. Bassett. 



Tale University Museum, May 27th, 1890. 



EXPLANATION OF PLATE IX. 



Leptjwisca concata, Hall, sp. 



Figure 1. — Ventral valve, interior; showing cardinal area and teeth; cardinal 



muscular lamellas, ; adductor impressions, a; vertical septum. 



Natural size. 

 Figure 2. — Posterior view of dorsal cardinal process, x 3. 

 Figure 3. — The same ; seen from above, x 3. 

 Figure 4. — Dorsal valve ; side view in outline, x 3. 

 Figure 5. — Dorsal valve, interior: showing cardinal processes, dental sockets, 



adductor muscular scars, median ridge, and spiral impressions. 



Natural size. Lower Helderberg group, Clarksville, N. Y. 



Strophalosia excavata, Geinitz. 



Figure 6. — Dorsal side of internal mould; showing muscular scars, septum, and 



reniform impressions. Natural size. 

 Figure 7. — Ventral view of another specimen, showing the adductor scars. 



Natural size. 

 Figure 8. — Profile of same. Natural size. Permian, Poesneck, Germany. 



Strophalosia Goldpussi, Munster. 



Figure 9. — Internal mould of ventral valve ; showing cardinal and adductor 

 muscular scars, and vascular lines. Natural size. Permian, 

 Trebnitz, Germany. 



Strophalosia scintilla, Beecher. 



Figure 10. — Specimen adhering to ventral valve of Productella pyxidata, Hall. 



Natural size. 

 Figure 11. — Specimen showing no spines; growing on Spirifer Marionensis, 



Shumard. x b. 

 Figure 12. — Specimen showing four spines; on Productella pyxidata, Hall x 6. 

 Figure 13. — Interior of ventral valve, on Syringothyris sp.; showing cardinal 



muscular scars, hinge area, teeth and six marginal spines, x 6. 



Chcteau limestone, Pike County, Missouri. 



Strophalosia radicans, Winchell, sp. 



Figure 14. — Interiors of two ventral valves; showing hinge-teeth and spines. 



x 2. Specimens of Spirorbis became attached after death of 



Strophalosia. 

 Figure 15. — Specimen preserving dorsal valve ; showing cardinal wrinkles, x 2. 

 Figure 16. — Interior of dorsal valve; showing adductor muscular scars, reniform 



impressions, cardinal process, and dental sockets, x 2. 

 Figure 17. — Spine enlarged to 10 diameters. Hamilton group, Little Traverse 



Bay, Michigan. Specimens figured, growing on Acervularia 



Davidsoni, E. and H. 



Strophalosia Keokuk, Beecher. 



Figure 18. — Interior of imperfect ventral valve showing muscular scars, septum 



and numerous long slender marginal spines, x 2. 

 Figure 19. — Small specimen preserving dorsal valve, x 2. 

 Figure 20. — Profile of same, x 2. 



Am. Jouu. Sci. — Third Series, Vol. XL, No. 237. — Sept., 1890. 



