188 SYSTEMATIC PALEONTOLOGY 



in the Eocene that it is possible that they both represent the same 

 Miocene species. Dr. Dall considers tliem identical but is in doubt as 

 to the horizon from which they came. 



It seems best to publish here the original fig'ures of A. mcgeei under 

 the original name in order to bring the question before the eyes of future 

 investigators. 



Length, 50 mm.; height, 48 mm. 



Occurrence. — Hanover County, Va. 



Collection. — Philadelphia Academy of Natural Sciences. 



Family PECTINIDAE. 



Genus PECTEN Miiller. 



Pectex choctayensis Aldrich. 



Plate XLIV, Pigs. 4, 5, 6. 



Pecten choctavennis Aldricli, 189.5, BulL Amer. PaL No. 2, p. 16, pi. v, fig. 7. 



Description. — " Shell suborbicular thin, depressed, finely closely rib- 

 bed, ribs showing throvigh the substance of the shell, imbricated near 

 the ventral margin and on the anterior slope; ears ribbed and ribs im- 

 bricated with fine oblique reticulations between." Aldrich, 1895. 



There are 40 to 50 ribs, which are lamellated, especially when old, 

 but sometimes when very young. The young shells from Alabama do 

 not show any lamellation. The ribs increase both by bifurcation and 

 intercolation. Camptonectes structure is a constant characteristic. 



Width, 23 mm.; height, 24 mm. 



Occurrence. — Nanjemoy Foemation. Popes Creek, 1^ miles above 

 Popes Creek. Aquia Foemation. Upper Marlboro, 1 mile northeast 

 of Piscataway, South East Creek (1 mile from Chester River). 



Collection. — Maryland Geological Survey. 



Pecten dalli Clark. 

 Plate XLIV, Figs. 7, 7a, 7b. 



Pecten rogersi Clark, ISD.t, Johns Hopkius Univ. Clrc, vol. xv, p. 5. 



Pecten rorjersi Clark, 1896, Bull. 141, U. S. Geol. Survey, p. 8.5, pi. xxxiv, flgs. 2a-2c. 



Pecten dalli Clark, 1898, Johns Hopkins Univ. Circ, vol. xviii, p. 18. 



Pecten (Pseudamusium) frontalis Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, 



pt. iv, p. 7.53. 

 Not Pecten rogersi Conrad. 



