STROPHALOSIA 145 



STROPHALOSIA KEOKUK Beecher 

 Plate XVIII, Figs. 17-18 



1890. Stroplwlosia Keokuk Beecher, Am. Jour. Sci. (3), vol. 40, p. 244, 



pi. 9, figs. 18-24. 

 1892. Strophalosia Keokuk Hall and Clarke, Pal. N. Y., vol. 8, pt. 1, pi. 



17A, figs. 5-7. 



Description. Shell small, attached to external objects by nearly the 

 entire pedicle valve, broader than long, subelliptical in outline, truncated 

 on the cardinal margin, the hinge-line a little shorter than the greatest 

 width. The dimensions of a nearly complete example are: length 3.8 

 mm., width 4.3 mm. 



Pedicle valve adherent to foreign objects, all the specimens observed 

 being attached to shells of Platyceras, its m/argin elevated and furnished 

 with numerous, slender, often crowded and rather elongate, procumbent 

 and attached spines which occur as commonly along the cardinal margin 

 as elsewhere ; cardinal area low and broadly triangular, with a narrowly 

 triangular delthyrium closed by a deltidium; the hinge-teeth well devel- 

 oped, not supported by dental lamellae. 



Brachial valve with a small umbonal convexity in front of the beak, 

 beyond which it becomes flat or concave ; the surface marked by concen- 

 tric lines of growth. 



Remarks. This species is of the type of 8. scintilla, but grows some- 

 what larger, and is often proportionally more elongate. It differs es- 

 pecially from that species in the more numerous, more elongate, and more 

 crowded spines of attachment which occur as commonly along the car- 

 dinal margin as elsewhere. 



Horizon. Keokuk (Crawfordsville shale, Indiana). 



STROPHALOSIA CYMBULA Hall and Clarke 

 Plate XIX, Figs. 35-36 



1892. Strophalosia cymbula Hall and Clarke, Pal. N. Y., vol. 8, pt. 1, 



pi. 17A, figs. 3-4, 8-9. 

 1897. Strophalosia cymbula Hall, 14th Rep. N. Y. State Geol., p. 355, 



pi. 7, fig. 5. 



Description. Shell of about medium size or smaller, not attached in the 

 mature condition, broader than long, the hinge-line nearly equaling the 

 greatest width, the cardinal extremities angular. The dimensions of one 

 of the co-types are : length 19.8 mm., width 22.5 mm., convexity of pedicle 

 valve 7 mm., height of cardinal area 1.6 mm. 



Pedicle valve moderately convex, the greatest convexity near the 

 middle, the beak a little distorted, the cicatrix small and inconspicuous, 

 the surface rather regularly convex except towards the cardinal ex- 



