244 THE DEVONIAN OF MISSOURI. 



Genus Beachia Hall and Clarke 



Beachia suessana (Hall) 



Plate 64, figures 16, 17 

 1857. Meganteris suessana Hall, Tenth Ann. Rept. N. Y. State Cab. Nat. Hist., p 



100. 

 1859. Rensselaeria suessana Hall, Nat. Hist. N. Y. Pal., vol. 3, p. 459, pi. 107, figs 



1-15, 1861. 

 1913. Rensselaeria {Beachia) suessana Schuchert, Geol. Surv., Md. Low. Dev., p 

 387, pi. 67, figs. 7-15. 



Description — Shell of medium size, a little longer than wide, elongate oval in outline 

 both shape and size being somewhat variable. The dimensions of an average sized indi- 

 vidual are: Length 27 mm., width 25 mm., the-greatest width well below the hinge line 

 Posterior margins sloping somewhat abruptly from the beaks, and terminating in 

 rounded cardinal extremities. Lateral margins of both valves abruptly inflected. 



Pedicle valve moderately convex, the greater convexity across the middle of the 

 shell. From the median line the shell slopes uniformly to the margins. Beak small, 

 angular, and well elevated above the opposite valve; apex pierced by a round foramen. 



Brachial valve about equally convex with the pedicle, the beak small, incon- 

 spicuous, and incurved slightly. 



The radiating markings which characterize Beachia suessana Hall, from the New 

 York Oriskany seem to be almost always absent in the specimens studied, probably due 

 to the condition of preservation, but a few obscure ones have been noticed. Concentric 

 growth lines mark the shells, these being most prominent near the anterior margin. 

 Punctuate shell structure poorly preserved. 



Remarks — Entire specimens and the separate valves occur. These correspond 

 closely to Beachia suessana Hall, but differ in having more distinctly rounded anterior 

 margins. There is also a close resemblance to Beachia amplexa Clarke, from the Grand 

 Greve limestone of the Gaspe region, but all the specimens which have come under 

 observation are considerably smaller than the former. 



This species in characterized by the inflected lateral margins, and the depressed 

 convex valves. 



Horizon — Lower beds. 



Figured specimens No. 27504, Walker Museum. . * 



Beachia ovalis (Hall) 



Plate 65, figure 1 



1857. Meganteris ovalis Hall, Tenth Ann. Rept. N. Y. State Cab. Nat. Hist., p. 101. 



1859. Rensselaeria ovalis Hall, Nat. Hist. N. Y. Pal., vol. 3, p. 458, pi. 106, figs. 2a-l, 



1861. 

 1913. Rensselaeria (Beachia) ovalis Schuchert, Geol. Surv., Md-. Low. Dev., p. 389, 

 pi. 67, figs. 17-19. 

 Description — Shell longitudinally ovate, with a well-rounded anterior margin. The 

 dimensions of an nearly perfect specimen are: Length 42 mm., width 36 mm.,- the great- 

 est width anterior to the middle of the shell. Lateral margins of both valves strongly 

 inflected. 



Pedicle valve depressed convex, the most prominent depression along the middle. 

 Beak well elevated above the hinge line and over the beak of the opposite valve. 



Brachial valve about equally convex with the pedicle, but less prominent along the 

 middle. Beak lower than that of the opposite valve and incurved below it. 



The simple, radiating costae, which are characteristic of the New York specimens 

 have not been observed. Due to the absence of the original shell surface and the punc- 

 tate shell structure has also been destroyed. 



