512 CRETACEOUS PALEONTOLOGY. 



Pormation and locality. — Tinton beds, Beers Hill cut, south of 

 Keyport (129^). 



Geographic distribution. — New Jersey, Mississippi, Wyoming, 

 Montana, Colorado. 



Genus LiThophaga Bolton. 



Lithophaga ripleyana Gabb. 

 Plate LVL, Figs. 9-12. 



1 861. Lithophagus Ripleycmus Gabb, Proc. Acad. Nat. Sci. 



Phil. (1861), p. 326. 

 1 861. Lithophagus asffinis Gabb, Pro'c. Acad. Nat. Sci. Phil. 



(1861), p. 327. 

 1864. Lithophagws aiffinis Meek, Check List Inv. Foss. N. A., 



Cret. and Jur., p. 10. 

 1864. Lithophaguis ripleyamns Meek, Check List Inv. Eoss. N. 



A., Cret. and Jur., p. loi. 

 1868. Lithophagws aMnis Con., Cook's Geol. N. J., p. 726. 



1875. Arcoperna carolinensis Con., Kerr's Geol. N. Car., App. 



p. 5, pi. I, fig. 6. 



1876. Lithophaga ripleyana Gabb, Proc. Acad. Nat. Sci. Phil. 



(1876), p. 311. 

 1886'. Lithodomus afUnis Whitf., Pal. N. J., vol. i (Monog. 



U. S. G. S., vol. 9), p. 66, pi. 17, figs. 2-3. 

 1886. Lithodomus ripleyana Whitf., Pal. N. J., vol. i (Monog. 



U. S. G. S., vol. 9), p. 67, pi. 17, figs. 4-5. 

 1905. Lithophaga affinis Johns., Proc. Acad. Nat. Sci. Phil. 



(1905). P- 13- 

 1905. Lithophaga ripleyana Johns., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 13. 



Description. — Shell more or less subcylindrical, sometimes 

 curved downward posteriorly, attaining' a length of 15 mm. to 

 20 mm. in full grown specimens, the width and thickness usually 

 about one-half the length. Anterior extremity of the shell 

 bluntly rounded, the beaks blunt, anterior or nearly terminal in 

 position; posterior extremity of the shell compressed. Dorsal 



