168 Systematic Paleoxtology — Middle Devonian 



Rhipiclomella penelope Hall and Clarke, 1892, Pal. N. Y., vol. vlli, pt. i, pp. 



211, 225, pi. vi, figs. 6-13; pi. vi A, figs. 10, (? 11). 

 lihipidomella penelope Schuchert, 1897, Bull. U. S. Geol. Surv., No. 87, p. 351. 

 RMpidomella penelope Clarke, 1903, N. Y. State Mus., Bull. No. 65, p. 298. 

 RMpidomeUa penelope Grabau and Shlmer, 1909, N. Am. Index Fossils, vol. 



i, p. 265, figs. 320f, g. 



Description. — SlicU large, oblate, proportions of length and breadth 

 about as four to five, ])lano-convex; hinge-line about two-fifths the width 

 of the shell. Yential valve depressed-convex above, sometimes a little 

 gibbous towards tlio umlio. fiat or often concave in the middle and below, 

 the front without sinuosity; the interior marked liy a subcircular or 

 broadh' ovate flabellate muscular impression, which occupies more than 

 half the length and breadth of the valve. Dorsal valve regularly convex, 

 the greatest convexity ahmit the center, with a very slight mesial depres- 

 sion or flattening along the center; the interior shows a prominent card- 

 inal process, which is continued in a median ridge sometimes nearly to 

 the front of the shell. Surface marked by fine radiating bifurcating 

 striae, which are arched upwards near the cardinal extremities, and 

 crossed by fine concentric lines as well as lamellose lines of growth, the 

 radiating striae frequently have the appearance of being broken or in- 

 terrupted, from the peculiar manner in which the pores open upon the 

 surface. 



This species is apparently rare in ]\Iaryland ; but a large, although 

 broken, specimen from Evitts Creek below Wolfe Mill is referred to it. 

 The species was identified by Hall from Cumberland, Md., and " a cast of 

 the dorsal valve " from that locality figured.' This species is quite similar 

 to R. vamixcmi but is generally considered larger, the striae are stronger, 

 the tubular openings of the striae are more elongate, and the muscular 

 area smaller and more rounded. 



Length, 33 mm. ; width, 38 mm. 



Occurrence. — Eomney Formatiox, Hamilton ^Iember. East bank 

 Evitts Creek below Wolfe Mill ( ?) . 



CoUections.—'Miwylnud Geological Survey; New York State Museum; 

 American Museum of Natural Histor}'. 



' Pal. N. Y., vol. i\', pi. vi, fig. 2m. 



