BRACHIOPODA. 81 



Stropheodonta inflexa Swallow 



Plate 13, figures 13-17 



1860. Strophodonta inflexa Swallow, Trans. St. Louis Acad. Sci., I, p. 637. 



1897. Stropheodonta navalis boonensis Schuchert, Bull. U. S. Geol. Surv. 87, p. 425. 



Swallow's description — "Shell semiellipsoldal, but a little wider in front, regularly 

 arched and coarsely costated. Ventral valve very convex, semiellipsoidal, wider in front, 

 highest near the center— regularly arched to the anterior margin, more abruptly at the 

 posterior extremity, and somewhat flattened near the beak — very regularly arched 

 transversely, but most abruptly on the obsolete mesial fold; ears very small, or obsolete; 

 beak small, depressed; area straight, narrow, impressed, and common to both valves; 

 umbo large and prominent. Dorsal valve semielliptical, less convex, slightly depressed 

 in front; lateral edges recurved and slightly arched where they meet the cardinal line; 

 cardinal line as long or shorter than the width of the shell, situated about one-third of 

 the length of the shell from the posterior extremity. Surface marked with large sub- 

 angular, unequal, irregular, granulated costae, increased by implantations and sub- 

 divisions; structure punctate. 



Length, 1.41; breadth, 1.21; depth of ventral valve, .83." 



Supplementary description — The specimens show the cardinal line about 1/5 the 

 length of the shell from the posterior extremity rather than 1/3 as stated by Swallow 

 but in other respects Swallow's description is good. The species seems good and is easily 

 distinguished from 5. cymbiformis Swallow by its coarser plications, much broader 

 arching, and broader form (length compared to breadth 9:10 to 10:10), and from S. 

 boonensis Swallow by its smaller plications, projecting umbo, shorter hingeline, and 

 greater convexity. The plications run 8 to 12 to the centimeter as compared with 12 to 

 18 in S. cymbiformis Swallow and 6 to 12 in 5. boonensis Swallow. It differs from S. 

 equicostata Swallow in having a much thicker shell, coarser plications, less prominent 

 auriculations, and greatest convexity directly below the hingeline. 



Occurrence — Snyder Creek shale, Montgomery and Callaway Counties. 



Stropheodonta nnneolaensis n. sp. 

 Plate 12, figures 18-21 



Shell of medium size, plano-convex to strongly concavo-convex, cardinal extremi- 

 ties blunt, hingeline little longer than the greatest width of the shell. Pedicle valve with 

 point of greatest convexity near the umbo, surface concave toward cardinal extremities, 

 area narrow. Brachial valve flat to strongly concave, area very narrow. 



The plications constitute the distinctive feature of the species. Three or four plica- 

 tions originate at the beak, and these form the dominant plications across the shell. 

 By bifurcation these give rise to about 8 or 9 each and they remain in distinct groups. 

 Outside these groups, on the cardinal extremities, the plications are faint or obsolete. 

 The shells of greater convexity have stronger plications nearer the cardinal extremities 

 than the less convex shells. 



The largest specimen in our collection measures 38 mm. in width, 24 mm. in length 

 and 6 mm. in height. A convex specimen measures 22 mm. wide, 20 mm. long and 

 8 mm. in height. 



Hall described S. plicata from Iowa and this species resembles it very closely. In 

 the Snyder Creek shale are young specimens that would be referred to S. plicata Hall 

 without question but the mature forms are 5. callawayensis Swallow. 



Figures 2, 4 and 5 of plate 14 are of immature forms of 5. demissa (Conrad), while 

 figure 6 of plate 13 seems to be an immature specimen of 5. boonensis Swallow. How- 

 ever, it is always difficult and in many cases impossible to refer the immature specimens 

 from the Snyder Creek shale to their proper species. In 5. plicata Hall, 6 to 8 plica- 

 tions originate at the beak and as they pass outward and bifurcate they do not form 



