108 CONTRIBUTIONS 



thickened, the callus being reflected at the middle of the 

 umbilicus ; umbilicus large, grooved ; whorls four, round- 

 ed ; mouth subovate, about three fourths the length of the 

 shell. 

 Length 5-20ths, Breadth .2, of an inch. 



Observations. In the roundness of the whorls it resem- 

 bles the minor described above, but differs in being globose, 

 while that shell is more elliptical. It has also a much 

 smaller callus. 



JV. gibbosa. Plate 4. Fig. 92. 



Description. Shell subovate, gibbous, smooth ; spire 

 rather produced ; substance of the shell thick ; callus 

 thick ; umbilicus large ; whorls five ; mouth sub-elliptical. 



Length 1.1, Breadth .9, of an inch. 



Observations. I have received but a single specimen of 

 this species. It is rather more elongated than usual in 

 the Notice. The upper part of the whorls being flattened 

 and the lower part being inflated, gives the shell a gibbous 

 appearance. 



JV". semilunata. Plate 4. Fig. 93. 



Description. Shell subglobose, smooth ; substance of the 

 shell rather thin ; spire slightly elevated ; suture rather 

 impressed; columella but slightly thickened, the callus 

 being reflected at the middle of the umbilicus ; umbilicus 

 large and grooved ; whorls five, inflated, slightly flattened 



