116 THE DEVONIAN OF MISSOURI. 



terminations of low ridges from above. Interpallial area pustulose on the cast. Five 

 specimens measure respectively 30, 32, 40, 44 and 48 mm. in length, and 29, 33, 37, 

 40 and 44 mm. in height." 



Remarks- — This species is abundant in some places in the Snyder Creek shale, and 

 especially so on Cow Creek at locality 2. The variety in size and shape is remarkable 

 and if the varieties were collected from several localities they might be referred to two 

 or more species. Some specimens are 1 }/% times as long as wide, while others are nearly 

 as wide as long. Some are 2/3 as thick as wide, while others appear thin and are less 

 than half as thick as wide. 



Occurrence — Callaway limestone and Snyder Creek shale. 



Paracycles lirata .(Conrad) 

 Plate 25, figures 9 and 12 



1838. Posidonia lirata Conrad, Geol. Surv. N. Y., Ann. Rept., p. 116, pi. (unnumbered), 



fig. 12. 

 1872. Posodonia (Paracyclas) lirata Hall and Whitfield, Twenty-fourth Ann. Rept. 



N. Y. State Mus. Nat. Hist., p. 200. 

 1885. Paracyclas lirata Hall, Pal. N. Y., V, pt. 1, Lamellibranchiata 2, pp. 441-442, 



pi. 72, figs. 2-19; pi. 95, fig. 19. 

 1901. Paracyclas lirata Kindle, Indiana Dept. Geol. Nat. Res., 25th Ann. Rept., 



pp. 673-674, pi. 15, fig. 10. 

 1903. Paracyclas lirata Clarke, N. Y. State Mus., Bull. 65, p. 483. 

 1909. Paracyclas lirata Grabau and Shimer, North American Index Fossils, I, p. 555, 



fig. 760b. 

 1911. Paracyclas lirata Cleland, Wisconsin Geol. Nat. Hist. Survey, Bull. 21, p. 118, 



pi. 25, figs. 6 and 7. 

 1913. Paracycles lirata Prosser and Kindle, Maryland Geol. Survey, Middle and 



Upper Devonian, pp. 277-278, pi. 34, figs. 11-14. 

 Hall's description — "Shell of medium size, subcircular or broadly elliptical; length 

 a little greater than the height; margins regularly rounded; cardinal line short, less than 

 half the length of the shell. Valves moderately convex below, becoming gibbous on the 

 middle and above; beaks anterior to the center, small, appressed, rising but little above 

 the hinge line; post-cardinal slope not defined. Surface marked by fine concentric 

 striae, and by strong subangular concentric ridges, which are more or less sharply 

 defined, depending upon the condition of the specimen and the nature of the matrix 

 in which the fossil is imbedded." 



Remarks — The specimens from central Missouri, though numerous, are all some- 

 what worn and specific reference is somewhat uncertain. The surface markings are not 

 as prominent as on Indiana and New York specimens but this may be due entirely to 

 wear. A well-marked difference between this species and P. elliptica Hall is the much 

 greater proportional thickness of P. elliptica Hall. P. lirata is a much smaller form. 



Occurrence — Abundant near the top of the Snyder Creek shale in Callaway County. 



