PAL^EONTOLOGICAL report of geological survey. 569 



each side, and terminate on the summit of the ribs, numbering, at 

 three lines from the beak, sixteen in the space of two lines; base se- 

 micircular, creuulated; height 1 .^% inches; width l.-j%V inches, 



Position and locality. From the limestone over the main Provi- 

 dence coal, No. 11, Hopkins county, Kentucky. 



MYALINA PERNAFORMIS. Cox. 

 (PI. VIII, fig. 8; right valve natural size.) 



Sub-quadrate; inequilateral; beak pointed, projecting beyond, and 

 moderately curved over the cardinal border; cardinal border nearly 

 straight; anterior margin and base rounded; posterior margin straight; 

 near which a prominent ridge gradually slopes to the front and base; 

 surface covered with strong concentric, somewhat fimbriating lines of 

 growth; length l. T W inches; width . r \\ inch. 



Position and locality. Common in the limestone over the main coal 

 No. 11, at Providence, Hopkins county, Kentucky. 



PLEUROTOMARIA DEPRESSA. Cox. 



(PI. VIII, fig. 19, 10a; natural size.) 



Small; lenticular; depressed; about five volutions scarcely eleva- 

 ted; nearly flat above; defined by a row of acutely pointed tuber- 

 cles, not so wide as the intervening notch; last whorl obtusely round- 

 ed below, bordered by a sharp edge, which has a narrow depressed 

 band above, only visible when the implanted tubercles are removed; 

 ornamented on the upper and lower side with obsolete lines of growth 

 bent backwards; umbilicus shallow; mouth notched; columella and 

 outer lip rounded; height .-j\% inch; width .-j%V inch ; spiral angle 

 130°. 



This species may at first easily be mistaken for P. sphcerulata, 

 Conrad, (P. coromda Hall; Stansbury's expedition to the Great Salt 

 Lake, 1852, page 413, pi. 4, fig. 6,) but is much more depressed, and 

 the angle of the last whorl more acute. The tubercles not so numer- 

 ous, and less elevated. 



Position and bcality. Common in the shale forming the roof of 

 No. 11 coal, at Bonharbour, Daviess County, and Airdrie, Muhlenburg 

 county, Kentucky. 



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