558 Systematic Paleontology 



Georgia; Chattahoochee River and Eufaula, Alabama; Chickasaw and 

 Pontotoc counties, Mississippi. Selma Chalk. Exogyra ponderosa zone, 

 Warrior River, Alabama ; Tennessee. Exogyra costata zone, Tombigbee 

 River, Alabama. 



OSTEEA MONMOUTHENSIS Weller 



Plate XXIII, Figs. 4, 5 



Ostrea monmouthensis Weller, 1907, Geol. Survey of New Jersey, Pal., vol. 

 iv, p. 442, pi. xliii, fig. 15. 



Description. — " Shell slightly oblique, subovate in outline, the dimen- 

 sions of the type specimen being: length 28 mm.; width 22 mm. Upper 

 valve depressed convex, nearly smooth, marked only by inconspicuous con- 

 centric lines of growth. Along the ventral margin the edge is folded into 

 sharply angular teeth which do not extend as plications into the body of 

 the shell, these tooth-like crenulations becoming smaller and at last dis- 

 appearing upon the lateral margins of the shell. Lower valve not known. 



"Remarks.- — It is with some hesitation that a species of so variable a 

 group of shells as the oysters has been proposed for a single specimen, but 

 it has not been possible to identify it with any of the described forms, and 

 it seems to be so distinct that it is probable that additional examples, 

 should they be found, could be recognized without difficulty. The shell 

 has much the general outline of the specimen referred to 0. crenulimargi- 

 nata by Whitfield, but that shell entirely lacks the characteristic denticu- 

 lation of the ventral margin of this species." — Weller, 1907. 



Type Locality. — Crawfords Corner, Monmouth County, New Jersey. 



Tlie species is fairly common in the Monmouth of Prince George's 

 County at Brightseat, but strangely enough it is represented by right 

 valves only. The form differs from the cover valve of 0. tecticosta not 

 only in the development of a marginal frill, but also in the heavier 

 texture of the shell, larger size, less cuneate outline, broader, lower 

 umbones and ligament area ; and in the character of the concentric 

 sculpture, the external surface of 0. tecticosta being adorned with densely 

 crowded concentric lamellae, while that of 0. monmouthensis is merely 

 roughened by more or less irregular concentric striations. 



