618 SYSTEMATIC PALEONTOLOGY 



A. Shell encrusted with concentrically laminated calcareous covering. 



Lithophaga ripleyana 



B. Shell not encrusted. 



1. Latitude of adult shell not exceeding 18 mm. 



a. Outline subcylindrical. 



i. Shell occurring in hard substances especially in the tests 



of larger bivalves Lithophaga concha fodentis 



ii. Shell occurring free or in clay tubes Lithophaga julice 



b. Outline transversely ovate Lithophaga lingua 



2. Latitude of adult shell exceeding 18 mm.; outline subcylindrical. 



Lithophaga twitchclH 



LITHOPHAGA EIPLEYAXA Gabb 

 Plate XXXVI, Figs. 4-6 



Lithophaga ripleyanus Gabb, 1862, Proc. Acad. Nat. Sci., Phila. for 1861, p. 



326. 

 Lithophaga ripleyanus Meek, 1864, Check List Inv. Fossils, N. A., Cret. and 



Jur., p. 10. 



Lithophaga ripleyana Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p. 311. 

 Lithodomus ripleyana Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 67, 



pi. xvii, figs. 4, 5 (ex parte). 



Lithophaga ripleyana Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 13. 

 Lithophaga ripleyana Weller, 1907, Geol. Survey of New Jersey, Pal., vol. 



iv, p. 512, pi. Ivi, figs. 9-12 (ex parte). 



Description. " Tube subcylindrical, nearly straight, gradually taper- 

 ing, broadest on the dorsal surface ; opposite face narrow, rounded ; 

 extremity abrupt, rounded and faintly subtrilobate. Shell subquadrate. 

 Beaks terminal, and projecting beyond the buccal end of the shell, very 

 much incurved, so as to appear somewhat spiral. Umbones broad, slightly 

 flattened in the middle. Cardinal margin straight anteriorly, depressed 

 posteriorly, merging into the anal border, which is subtruncate and most 

 prominent above. Basal edge broadly emarginate. Surface marked by 

 numerous, irregular, concentric lines." Gabb, 1860. 



Type Locality. Big Timber Creek, between Gloucester and Red Bank, 

 New Jersey. 



Form gregarious, rudely cylindrical, constricted mesially; protective 

 covering built up of thin, concentric layers of calcite, usually conforming 

 rather closely to the outline of the shell ; shell itself very thin, nacreous in 

 texture; umbones terminal, prosogyrate, well rounded at their tips; 

 anterior portion inflated, truncate; shell, in the majority of the indi- 



