138 Systematic Paleontology — Middle Devonian 



Steopheodonta (Douvillina) inaequistriata (Conrad) 

 Plate X, Figs. 2-5 



Strophomena inaequistriata Conrad, 1S42, Jour. Acad. Nat. Sci., Phila., vol. 



viii p. 254, pL xiv, fi?. 2. 

 Strophoviena inaequistriata Hall, 1843, Geol. N. Y., pt. iv, p. 201, fig. 4 on 



p. 200. 

 Strophoviena (Strophoclonta) inaequistriata Hall. 1857, Tenth Rep. N. Y. 



State Cab. Nat. Hist., p. 142. 

 Strophodonta inaequistriata Hall, 1867, Pal. N. Y., vol. iv, p. 93, pi. xii, figs. 



6-8; p. 106, pi. xviii, figs. 2a-2fc. 

 Stropheodonta {Douvillina) inaequistriata Hall and Clarke. 1892, Pal. N. Y., 



vol. viii, pt. i, p. 289, pi. xiv, figs. 1-6; pi. xv B, fig. 9. 

 Stropheodonta inaequistriata Schuchert, 1897, Bull. U. S. Geol. Surv., No. 87. 



p. 422. 

 Douvillina inaequistriata Clarke, 1903, N. Y. State Mus., p. 231. 

 Stropheodonta inaequistriata Grabau and Shinier, 1907, N. Am. Index 



Fossils, vol. ii, p. 217, fig. 262. 



Description. — Shell generally less than medium size and somewhat 

 semioval in outline; hinge-line longer than the width of the shell below; 

 extremities acute, sometimes auriculate. Earely, the sides are nearly 

 straight below the auriculate extremities, the basal curve rather straight- 

 ened on each side and produced in a subnasute extension in the middle. 

 Ventral valve usually regularly convex, often more gibbous in the middle 

 and abruptly arched toward the hinge-line, depressed-convex on the disc, 

 with the margin towards the front more abruptly curving; the beak is 

 small, scarcely prominent on the hinge-line. Cardinal area is narrow- 

 linear, extending to the extremities of the hinge-line, striated vertically, 

 with the inner margins crenulate from one-half to two-thirds the length 

 from the beak to the extremities; no foramen. Dorsal valve moderately 

 to deeply concave; cardinal area scarcely more than one-half as wide as 

 on the ventral valve. Surface of the entire shell marked by slender dis- 

 tant elevated striae, which are increased by interstitial additions, the 

 interspaces occupied by much finer closely arranged striae, which are 

 scarcely visible to the naked eye, and crossed by fine concentric striae. 

 The muscular markings are well shown on both valves although subject 

 to considerable variation; while just without the muscular areas the 

 interior surface is rather strongly pustulose, and beyond this it is finely 

 pustulose in lines corresponding to the external striae. 



