342 THE PALEONTOLOGY OF MINNESOTA 



[Lingula philomela. 



"The width at one-fourth the length from the beak is usually one-fourth less 

 than it is at one-sixth the length from the front margin. The following are the 

 measurements of a specimen of the ordinary form : 



"Length, 12| lines; width at 3 lines from beak, 6A lines; width at 2 lines from 

 front, 9 lines. 



"The largest specimen found measures nearly one inch and a half in length." 



The surfaces of the valves from the mid-length to the anterior margin are 

 marked by a few prominent radiating, continuous, or intermittent striations. The 

 concentric growth lines in passing the radiating striae are more or less reflexed 

 posteriorly. 



Of this species we have seen but a single example in a good state of preserva- 

 tion. It was discovered some years ago by Mr. W. H. Shelton, and is from the 

 Trenton Shales near St. Charles in Winona county, Minnesota. The rather strongly 

 convex valves without indications of a median depression, and the gradually diverg- 

 ing lateral outline, will readily separate it from Linpula quadrata Hall,=L. rectilater- 

 alis Emmons. 



Formation and locality. From the Trenton shales, in section six, Fremont, Winona county, Minne- 

 nesota. Also in the Black River formation of Murray bay, lower St. Lawrence river, Canada. 



Mus. Reg. No. 4973. 



LINGULA PHILOMELA Billings. 



PLATE XXIX, FIGS. 7,8. 



1862. Lingula philomela BILLINGS. Paleozoic Fossils, vol. i, p. 49, flg. 53. 



1863. Lingula philomela BILLINGS. Geology of Canada, p. 161, flg. 133. 



1892. Lingula philomela HALL. Palaeontology of New York, vol. viii, pt.i, pi i, flg. 8. 



Original description. "Very elongate oval; width a little less than half the 

 length ; front margin rather narrowly rounded with a small space in the middle 

 straight or sinuate ; sides for about two-thirds the length straight or very gently 

 convex ; the apical extremity appears to be obtusely angular, bub this still remains 

 doubtful, as no specimens with this part perfect have been collected. The shell is 

 rather strongly convex, most prominent at or about the mid-length. There is a 

 shallow concave sinus extending all along the median line from near the apex to 

 the front margin. Surface with fine crowded imbricating striae of variable size, 

 the smaller just visible to the naked eye, and the larger partaking of the nature 

 of squamose interruptions of growth. Color in the black limestone black. A 

 specimen in gray limestone showing the interior in a state of exfoliation is light 

 grayish-brown, but this may be owing to some circumstance in the fossilization of 

 the shell. 



"Length 16 lines; width 7 lines." 



