333 



Bulletin 5 53 



FOSSIL SHELLS. 1 47 



parently but little changed ; by pressure of the 

 nail it is readily separated into flaxy filaments. 



3. L. subobliqiia. Orbicular, slightly oblique, a 

 little compressed ; teeth prominent ; lunule not 



distinct. 



Description. Shell concentrically wrinkled ; a 

 little oblique forwards, the most prominent part 

 of the basal curvature being anterior to the mid- 

 dle ; no appearance of an -impressed line on the 

 margins, which are rounded, the hinge margin 

 being rectilinear for a short distance : hmide none, 

 or consisting only of a. slightly impressed line : 

 beaks slightly prominent : imtscitlar impressions 

 dilated, submarginal : cardinal teeth prominent, the 

 larger one with a groove : lateral teeth none. 



Length four-fifths of an inch, breadth nearly the 



same. 



4. L. cribraria. PI. xiii. fig. i. Orbicular, con- 

 vex, with numerous longitudinal costae, and distinct 

 elevated concentric lines. 



Description. Shell with close set, longitudinal, 

 equal, granulated ribs, and more or less elevated, 

 distinct, concentric lamellae : hi^ige margin obtusely 

 and not prominently angulated at its anterior and 

 posterior terminations : anterior margin with a di- , 

 lated slightly impressed, and not very obvious 

 groove : lunule oblong-oval, very distinct, the 

 edge near the beaks extending inwards beside the 

 primary teeth : lateral teeth very distinct, the pos- 

 terior one placed nearly under the middle of the ^^^ ^ 



[J. A. N. S., Phila., ist Ser., VoL IV, 1824.] .'<=.Vv.C.On!^n inS|/>^, 



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