242 THE DEVONIAN OF MISSOURI. 



Superfamily Terebratulacea 



Family Centronellidae 



Genus Centronella Billings 



Centronella glansfagea (Hall) 



Plate 64, figures 4-7. 



1857. Rhynchonella glansfagea Hall, N. Y. State Cab. Nat. Hist., Tenth Ann. Rept., 



p. 125, figs. 1-6. 

 1867. Centronella glansfagea Hall, Nat. Hist. N. Y. Pal., vol. 4, p. 399, pi. 61a, figs. 



1-21, 25-26. 

 1908. Centronella glansfagea Clarke, Mem. N. Y. State Mus., vol. 9, pt. 1, p. 163, pi. 

 25, figs. 1-4. 



Description — Size of shell variable, small to medium, sub-quadrate or .spoon- 

 shaped, the cardinal margins sloping abruptly to the beaks; length greater than the 

 width, the maximum width about midway between the beak and anterior margin. The 

 dimensions of two different individuals are: Length 20 mm., width 14 mm. and length 

 14 mm., width 10 mm. 



Pedicle valve larger than the brachial, convex, usually sub-carinate along the 

 middle, the surface sloping steeply to the lateral margins. Beak considerably elevated 

 above that of the opposite valve, abruptly curved, and extended in a horizontal plane 

 so that the apex lies well beyond the brachial valve. 



Brachial valve smaller than the pedicle, depressed convex, towards the anterior 

 margin becoming flatter and forming a faintly defined mesial sinus which includes the 

 entire width of the shell. A small extremely carinated specimen shows a well defined 

 sinus extending from beak to anterior margin. Beak small, incurved below the opposite. 



Surface smooth, shell substance very finely punctate. The concentric lines of 

 growth are especially prominent on the brachial valve. 



Remarks — The few specimens studied seem to be fairly constant in their char- 

 acters, and show no marked deviation from the New York examples. 



Horizon — Upper beds. 



Figured specimens No. 27507 Walker Museum. 



Genus Rensselaria Hall 



Rensselaeria ovoides (Eaton) 



Plate 64, figures 8-12. 



1832. Terebratula ovoides Eaton, Geological Textbook, p. 45. 



1859. Rensselaeria ovoides Hall, Nat. Hist..N. Y. Pal., vol. 3, p. 456, pi. 104, figs. 1-4; 



pi. 105, figs. 1-6. 

 1900. Rensselaeria ovoides Clarke, Mem. N. Y. State Mus., vol. 3, No. 3, p. 39, pi. 



5, figs. 17-19. 

 Description — Shells varying in size from medium to large, but in no case do they 

 attain the large proportions of the New York examples. Some specimens are extremely 

 gibbous, others less so. Both valves are incurved toward the lateral margins, and pro- 

 duce a conspicuous flattening of the shell. There is a distinct variation from elongate- 

 oval or spatula-shaped gibbous forms to shorter and less gibbous ones. An average 

 mature specimen is considerably longer than broad and measures about 62 mm. in 

 length, and 40 mm. across its greatest width which is well above the middle of the shell. 

 The dimensions of a smaller individual, and this size seems to be abundant, are: Length 

 35 mm., width 20 mm. 



