146 THE DEVONIAN OF MISSOURI. 



face marked by twenty or more simple plications on each side of the fold and sinus 

 and the principal ones, especially of the ventral valve, are often marked along the 

 center by a threadlike groove; toward the front are numerous, often imbricating, con- 

 centric lines." 



Remarks — The Missouri specimens are poorly preserved. They are fairly abundant. 

 Hall states that there are 20 to 30 plications on either side of the fold and sinus while 

 the Missouri specimens have only sixteen. The Missouri specimens show no radiating 

 striations and they lack the thread-like groove along the top of the larger plications. 

 It may be that the preservation obscures this feature. The specimens intergrade with 

 S. pennalus ' (Atwater) to such an extent that only the longer shells with high areas can 

 be definitely distinguished 



Occurrence — St. Laurent limestone, 3 miles south of St. Marys. 



Spirifer granulosus (Conrad) 



Plate 33, figures 1, 2 and 10 



1839. DeUhyris granulosa Conrad, Third Ann. Rep. Geol. Survey N. Y., p. 65. 

 1857. Spirifer granuhfera Hall, Tenth Rep. N. Y. State Cab. Nat. Hist., p. 163. 

 1867. Spirifira granulifera Hall, Pal. New York, IV, pp. 223-225, pi. 36, figs. 1-13; 



pi. 37, figs. 1-4. 

 1897. Spirifer granulosus Schuchert, Bull. U. S. Geol. Surv., 87, p. 391. 

 1901. Spirifer granulosus Kindle, Indiana Dept. Geol. Nat. Res., 25th Ann. Rep., 



pp. 640-641, pi. 9, figs. 2, 2a, 2b. 

 1909. Spirifer granulosus Grabau and Shinier, North American Index Fossils, I, p. 



328, fig. 417. 

 1913. Spirifer granulosus Prosser and Kindle, Maryland Geol. Surv., Middle and 



Upper Devonian, pp. 190-192, pi. 18, figs. 1-6. 

 Hall's description — "Shell more or less ventricose in its different stages of growth, 

 somewhat transversely oval, semi-elliptical or subquadrate; hinge line about equal 

 to the width of shell; cardinal extremities rounded or subangular. Surface plicated. 



Ventral*valve scarcely so gibbous as the dorsal valve, its greatest convexity about 

 therniddle of its length, and curving regularly to the margins;, beak much elevated above 

 that of the opposite valve and arching over the fissure but scarcely incurved; mesial 

 sinus shallow, concave, usually well defined and reaching distinctly to the apex. Area 

 high concave elevated and continuing to the hinge extremities; foramen large, reaching 

 to the apex and sometimes partially filled by the thickening of the dental plates. Dorsal 

 valve the more gibbous, the greatest convexity in the middle and curving regularly to 

 the front and lateral margins and usually a little flattened or concave towards the cardi- 

 nal extremities; mesial fold prominent, rounded, with a longitudinally depressed line 

 along the middle. Area narrow, vertical or in the plane of the longitudinal axis. The 

 surface is marked by from fifteen to seventeen rounded or subangular plications on each 

 side of the mesial fold and sinus; and these are crossed by distinct concentric striae, 

 which become strongly imbricating, or are marked in strong imbricating lines of growth 

 toward the margin. In well preserved specimens there are distinct radiating striae. 

 In many of the silicified specimens, however, both the radiating and concentric striae 

 are partially or entirely obliterated. The interior of the ventral valve shows two short 

 or rather strong teeth, with the ventral portion quite solid. The dental plates reaching 

 to the bottom of the cavity of the shell, curve slightly outwards and partially enclose 

 an oval muscular area which, in its upper part is divided by a short prominent median 

 crest. In some silicified specimens the conical spires are partially preserved. The 

 crura are widely separated at their bases and converging somewhat abruptly, curve 

 into the dorsal valve, making twelve or more turns, and producing a short, strqng.spire. 

 In well-preserved specimens the mesial fold and sinus are usually sharply defined but 

 in some of the more gibbous forms the sinus is very broad and one or two of the plica- 



