150 THE DEVONIAN OF MISSOURI. 



1901. Pterinea flabella Kindle, Indiana Dept. Geol. Nat. Res.. 25th Ann. Rep., p. 668. 

 1903. Pterinea flabella Weller, Geol. Surv. New Jersey, vol. 3, p. 378, pi. 52, fig. 12. 

 1909. Pterinea (Comellites) flabellum Grabau and Shinier, North American Index 



Fossils, I, pi. 421, fig. 551. 

 1913. Pterinea flabellum Prosser and Kindle, Maryland Geol. Surv., Middle and 

 Upper Devonian, pp. 250-251, pi. 29, figs. 1-4. 

 Hall's description — '"Shell large; broad or narrow ovate, oblique rarely erect; 

 length from two-thirds to nearly equal the height; and in some extravagant forms the 

 height is about double the length; the greatest length below the middle; anterior and 

 basal margins regularly curved; the posterior margin from a little above the base, follows 

 a nearly straight line to the beak. 



Left valve more or less convex, often gibbous and arcuate. Right valve flat or 

 concave, with a little convexity on the umbo; arcuate, to correspond with the curvature 

 of the opposite valve. 



Hinge line straight, extended uoon the posterior side; length greater than the length 

 of the valve. 



Beak of left valve acute, rounded, situated near the anterior extremity of the hinge, 

 curving forwards over the hinge margin. In rare instances the beak does not extend 

 quite as far as the margin of the hinge. Umbo of the left valve prominent, gibbous 

 limited by the sulci of the cardinal expansions, and subtending an angle of from 30° to 

 60°. Beak of the right valve depressed, rounded, not rising above the hinge; umbonal 

 region depressed-convex, gradually merging into the body of the valve, which is con- 

 cave below. 



Wing large, triangular, nearly flat, varying in proportions, defined (in the left valve) 

 by the post-cardinal slope; margin concave; extremity acute, rounded. Ear of left 

 valve a simple rounded convex lobe or auriculation, defined by a distinct, broad, rounded 

 sulcus; margin rounded above, sinuate at its junction with the valve, forming the 

 byssal sinus. The cardinal expansions of the right valve are similar in dimensions to 

 those of the opposite valve; nearly in the same plane with the body of the shell, and 

 defined only by the surface striae and the sinus. 



Test strong, nacreous, often having a thickness of more than one millimetre. Left 

 valve marked with from six to ten or twelve strong rounded rays, which originate at or 

 near the beak and continue simple to the margin. The interspaces are marked by smaller, 

 alternating costae, increasing by interstitial addition as the shell increases in size. The 

 surface is also ornamented with strong, elevated, concentric lamellose striae of growth, 

 which are more or less distinctly bent backwards over the stronger radii. The cardinal 

 expansions are marked with rays; those on the ear in well-preserved specimens, are 

 stronger than on the wing. 



In the right valve the surface is marked with concentric lines which are more 

 crowded on the cardinal expansions, and with a few strong radii on the wing, which 

 are sometimes quite obsolete." 



Remarks — This is a common form in the sandstone member of the St, Laurent on 

 Little Saline Creek. Only one fragmentary specimen has been collected from the 

 St. Laurent limestone. The specimens are all fragmentary. 



Genus Glyptodesma Hall 



Glyptodesma cf. ereclum (Conrad) 

 Plate 36, figure 7 

 1842. Aviculata erecta Conrad, Jour. Acad. Nat. Sci., Phila., p. 238, pi. 12, fig. 5. 

 1884. Glyptodesma erectum Hall, Pal. New York, vol. V, pt. 1, Lamellibranchiata, I, 

 pp. 153-155 pi. 11 figs. 1-10; pi. 12 figs. l-9;pl. 13 figs. 1-4 12-15;pl.25 figs. 14- 

 17; pi. 86, figs. 1-8; pi. 87, figs. 1-3. 

 1909. Actinodesma erectum Grabau and Shimer, North American Index Fossils, I, 

 p. 423, fig. 553, a, b. 



