324 Systematic Paleontology 



" Shell subsemicircular, about four-fifths as long as wide. Ventral 

 valve concave : beak not projecting beyond the hinge. Dorsal valve con- 

 cave near the umbo, very convex near the middle : beak not elevated above 

 the cardinal margin ; sides somewhat contracted below the extremities of 

 the hinge. Hinge-line straight, nearly or quite equalling the greatest 

 width of the shell, finely crenulated. Area narrow, linear, vertically 

 striated. Foramen nearly closed, with a narrow prominent callosity along 

 the center. Surface marked by strong sharp stria?, M^iich increase by 

 bifurcation and interstitial addition, becoming rapidly more numerous 

 and finer towards the margins, and are distinctly punctate in the best pre- 

 served specimens." Hall, 1859. 



Length about 3.85 cm.; width about 4.5 cm. 



A careful comparison of Albany County, New York, material of S. 

 cavumbona Hall reveals no characters not possessed by S. punctulifera 

 Conrad as redefined by Hall. The S. euglypha Eoemer ^ Foerste told the 

 writer was derived from the Louisville limestone zone, and does not belong 

 to this species. 8. cavumhona Meek and Worthen ^ may be regarded as a 

 good variety under the name rcdilateraria proposed in the same place. 

 It should be written 6'. punctulifera rectilateraria. On account of these 

 changes in the synonymy the complete bibliography of *?. piinctulifcra has 

 been given above. 



Occurrence. — Heldeuberg Formation, Coeymans Member. Dawson, 

 Corriganville, Devil's Backbone. jSTew Scotland Membek. Dawson, 

 Devil's Backbone, Corriganville, Maryland ; Warren Point, Pennsylvania. 



Collection. — Maryland Geological Survey. 



Strophonella keyserensis n. sp. 



Plate LIX, Fig. 11 



Description. — Shell subsemicircular, concavo-convex, resupinate; about 

 four-fifths as long as wide. Dorsal valve more convex than ventral valve, 

 concave near umbo. Hinge-line usually somewhat greater than width of 



' SiL Fauna d. w. Tenn., 1860, p. G6, pi. v, fig. 3. 



= Geol. Surv. 111., vol. iii, 1868, p. 374, pi. vii, fig. 10. 



