PLEIOCENEFOSSILS. 49 



Cardinal teeth coarse, oblique. The greatest length of the shell is towards the umbones, 

 which gives the shell a somewhat auriculated contour; a character which distinguishes 

 the species from both P. tricenarius and P. parilis. From the former it is also distin- 

 guished by its more robust teeth. Occurs in the Meiocene of Petersburg, Va., and in 

 North-Carolina. 



Plate XVII. Fig. 3, Exterior left valve; interior, hinge and teeth of right valve. 



Locality. Sumter District. 



Museum, College of Charleston. 



PECTUNCULUS QUINQTJERTJGATUS.— Con. 

 Plate XVII. Fig. 4. 



Pectunculus quinquerugatus, Con., Am. Jour. Sci., Vol. 4, p. 346. 

 Pectunculus quinquerugatus, Con., Foss. Ter. For., p. 63, pi. 34, fig. 3. 



P. testa tenui, sub-orbiculata, sub-cequilaterali, radiatim tenussime striata; costis depressis; 

 umbonibus, latere buccali rugato. 



Description. Shell thin, nearly orbicular, almost equilateral, concentrically wrinkled, 

 radiately and very finely striate ; ribs depressed ; buccal side of the umbones wrinkled. 



This fine species is the largest of the genus found in our tertiary rocks. It is thin for 

 its size. The teeth are rather small, curved upon a narrow hinge-plate. But the singular 

 characteristic which separates it from the other species, is the wrinkles on the side of the 

 umbones. It occurs also in North-Carolina. 



Plate XVII. Fig. 4, Exterior of left valve; interior, hinge and teeth of right valve. 



Locality. Waccamaw. 



Museum, College of Charleston. 



