798 NORTH AMERICAN INDEX FOSSILS. 



subsutural flattening; spirals numerous, finely nodulated; no ribs; 

 outer lip expanded and toothed; columella with three folds. 



Aquia formation of Atlantic coast ; Chickasawan of Gulf coast. 



612. C. conradiana Dall. (Fig. 1 171.) Oligocenic. 

 Whorls somewhat flattened on the side, and with a rather pro- 

 nounced subsutural flattening; ribs strong, distant; spirals of 

 almost equal strength, numerous; columella with three sharp 

 plaits. 



Chipolan beds of eastern United States. 



613. C. alternata Conrad. (Fig. 11 72, b, c.) Miocenic. 

 Round-whorled, subglobose; with strong round ribs, thicker in 



the middle, crossed by sharp spirals; aperture broad; outer lip 

 lirate; columella with two strong folds. 

 Chesapeakean of Atlantic coast. 



614. C. lunata Conrad. (Fig. 11 72, of.) Miocenic. 

 Higher spired than preceding though low coiling; ribs farther 



apart; aperture drawn out into a somewhat longer canal. 

 Chesapeakean of Atlantic coast. 



615. C. (Trigonostoma) biplicifera Conrad. (Fig. 1172, e.) 



Miocenic. 



Larger, with a well developed subsutural shelf, rather strongly 

 channeled; coarse irregular ribs on the body whorl; the aperture 

 with both anterior and posterior canaliculation ; the outer lip lirate ; 

 the columella with strong callus and two plications. 



Chesapeakean of Maryland. 



Family Terebrim: Adams. 

 CXCII. Terebra Lamarck. 

 Shell usually high-spired, slender and acuminate, whorls regu- 

 larly enlarging, body whorl not inflated; aperture with short, 

 curved canal, generally sharp or slightly canaliculate posteriorly. 

 Surface of whorls smooth or ribbed; a depressed spiral occurs a 

 short distance below the suture constricting off a subsutural band ; 

 this is weak or wanting in the subgenus Acus, Humphrey. Ter- 

 tiary-Recent. 



616. T. unilineata Conrad. (Fig. 1173,0, b.) Miocenic. 

 Constricting spiral prominent, the space between it and the suture 



