GASTROPODA— ADEORBIIDJE—NERITOPSIDJE. 705 



330. T. milium Dall. Miocenic-Pliocenic. 



Of three whorls ; suture not impressed ; open umbilicus of 

 young bounded by obscure angular ridge ; in adult, with callus 

 having concave surface ; aperture nearly round. 



Chesapeakean of North Carolina, Pliocenic of Caloosahatchie and 

 Shell Creek, Florida. 



XCIV. Adeorbis Wood. 

 In form like the preceding, but with large open umbilicus and 

 surface generally spirally sculptured, often angulated, and some- 

 times ribbed. Oligocenic-Recent. 



331. A. supranitidus Wood. (Fig. 1015.) 



Oligocenic-Recent. 



With three strong carinae, one medially placed, 

 and one each on upper and lower side ; surfaces 

 between mostly flat. 



Oligocenic of Santo Domingo and of Florida 

 (Chipola beds) ; Chesapeakean of Maryland and 

 North Carolina ; Pliocenic (Waccamaw beds) of 

 South Carolina and of Europe. Recent on both 

 sides of the Atlantic. 



332. A. concavus Lea. Miocenic-Pliocenic. 

 Smooth, except for angulated periphery, with 



flat spire and strongly embracing whorls, large 

 part of aperture being applied to the body. 



Chesapeakean of Virginia and North Caro- 

 lina ; Pliocenic of North Carolina and Florida. 



Fig. 1015. Ade- 

 orbis supranitidus, 

 much enlarged. 

 (Md. Survey.) 



Family Neritopsid/e Fischer. 

 XCV. Neritopsis Grateloup. 



Naticoid shells, non-umbilicate, with depressed spire and large 

 body whorl ; surface with ribs and spirals ; inner lip thick, angu- 

 larly emarginate in the middle. Operculum calcareous, not spiral. 

 Triassic-Recent. 

 333. N. biangulata Shumard. Cretacic. 



Depressed, wider than high, spire about one fifth of the height 

 of shell. Volutions three to three and one half, angulated, with 

 narrow, flat shoulder, declining very gradually from angle of 



