192 THE DEVONIAN OF MISSOURI. 



Order Telotremata 



Superfamily Rhynchonellacea 



Family Rhynchonellidae 



Genus Rhynchotrema Hall 



Rhynchotrema formosa (Hall) 

 Plate 48, figures 20-22 



Rhynchonella formosa Hall, 1857, 10th Ann. Rept. N. Y. State Cab. Nat. Hist., p. 76, 



figs. 1-5. 

 Rhynchonella formosa Hall, 1859, Pal. N. Y., vol. Ill, p. 236, pi. XXXV, figs. 6 a-i, 



k-p, r-u, x, y, 1861. 

 Stenocisma formosa Hall, 1867, Pal. N. Y., vol. IV, pt. I, p. 334. 

 Sienochisma formosa Hall and Clarke, 1893, Pal. N. Y., vol. VIII, pt. II, pp. 187-189; 



pi. LVI, figs. 41-45, 1894. 

 Rhynchotrema formosum Schuchert, 1897, U. S. Geol. Surv., Bull. 87, p. 369 

 Stenochisma formosa Shimer, 1905, N. Y. State Mus., Bull. 80, p. 245. 

 Stenochisma formosa Maynard, 1913, Md. Geol. Surv,, L. Dev., p. 349, pi. LXII, figs. 



25-29. 



Description — "Shell subtriangular or transversely oval; lateral margins forming an 

 angle at the beak of about 90 degrees to 110 degrees. Ventral valve somewhat more 

 depressed than the opposite; beak prominent, arched, not strongly incurved. Dorsal 

 valve larger, declining with a gentle curve towards the margins; beak incurved. Sur- 

 face marked by twenty to twenty-four simple angular plications on each valve, from 

 two to four of which in the middle are coarser and depressed in the ventral valve, having 

 a corresponding number abruptly elevated upon the dorsal valve; concentrically marked 

 by fine closely arranged striae." — Hall, 1859. 



Remarks — But one specimen has been observed. 



Genus Eatonia Hall 



Eatonia singularis (Vanuxem) 



Plate 49, figures 1, 2 



Atrypa singularis Vanuxem, 1842, Geol. N. Y., Rept. 3rd Dist., p. 120, -fig. 3. 

 Eatonia singularis Hall, 1859, Pal. N. Y. vol. Ill p. 243, pi. XXXVIII, figs. 14, 15 a, 



b, 16 a-c, 17 a-d, 18, 19 a, b, 20, 1861. 

 Eatonia singularis Hall and Clarke, 1893, Pal. N. Y., vol. VIII, pt. II, p. 206, pi. LXI, 



figs. 13-16, 1894. 

 Eatonis singularis Weller, 1903, Pal. N. J., vol. Ill, p. 311, pi. XXXVI, figs. 24-27. 

 Eatoma singularis Shimer, 1905, N. Y. State. Mus., Bull. 80, p. 245. 

 Eatonia singularis Schuchert, 1913, Md. Geol. Surv., L. Dev., p. 371, pi. LXV, figs. 



21, 22. 



Description — "Shell wider than long, varying in form from ovate to transversely 

 elliptical or rhomboidal; hinge line very slightly declining from the beaks. Ventral 

 valve depressed convex in the middle towards the beak, and concave between the 

 centre and the deflected margins; and below the middle, extended into a deep broad 

 sinus, which is prolonged and turned upwards in front at right angles to the longi- 

 tudinal direction of the shell; beak small, closely incurved. Dorsal valve convex, some- 

 times gibbous, and sloping abruptly to the margins; having a strong mesial fold be- 

 ginning above the centre, and produced in a broad flattened and greatly elevated ex- 

 tension. Surface marked by fine radiating striae, which, in well-preserved specimens, are 



