NORTH-CAROLINA GEOLOGICAL SURVEY. 



287 



FIG. 208. 



P. ARATUS. (Fig. 208.) 



This is the smallest species of this gernis be- 

 longing to the shell marl. It is also one of the 

 most common. P. passus and P. quinqueruga- 

 tus are also common in certain localities. 



LEDA ACTJTA. (Fig. 208A.) 



FlG - 208A - Shell small, thick, inflated pos- 



^/ sssss ^ i \ /(^^fc^*. teriorl j; margin acute or beaked, 



<?: ) 1 ^^^ slightly open ; anterior margin, 



short rounded ; surface concen- 

 trically striated. This fossil re- 

 sembles nucula, but it is not pearly in the interior, and its ab- 

 dominal margin is smooth. 



cute, 



NUCULA PROXn 18 . about *208B.) 



Shell small, 6^, ra ^ ( mooth, interior pearly ; 

 anterior margin short ; posterior side elongat- 

 ed, obtuse ; margin crenate. ET. limatula is 

 more common in the marl beds of this State 

 than the N. proxima ; miocene. 



FIG. 20SB. 



FAMILY CHAMACEDAE. 



The shell is thick, inequavalve, with sub-spiral beaks, hinge 

 teeth 1 2, muscular impression one, and large ; reticulated 

 palleal line simple. 



CHAMA. 



The shell is attached to other bodies by its left umbo : 

 hinge-tooth of the free valve thick, curved, and received be- 

 tween the teeth of the other valve. 



CHAMA ARCINELLA. (Fig. 209.) 



Shell thick, or orbicular-cordate squamose ; the radiating 

 ribs spinose, strong, tubular or folded ; intervening space 

 coarsely punctate and rugose. Common in the marl bed at 

 Elizabethtown, Bladen county. 



