The Nautilus. 



Vol. XXIX. SEPTEMBER, 1915. No. 5 



APICAL CHARACTERS IN SOMATOGYRUS, WITH DESCRIPTIONS 

 OF THREE NEW SPECIES. 



BY BRYANT WALKER 



(Continued from page 4^1) 



S. nanus Walker. Apical whorl prominent, blunt, flatly 

 rounded, only slightl}'' everted, not constricted by the suture, 

 very rapidly enlarging, a peculiarity apparently confined to a few 

 species. Sculpture punctate above and lirate below. 



S. obtusus Walker. Apical whorl obtuse, flatly rounded, not 

 everted, npt constricted by the suture, which is well impressed, 

 but vertical. Sculpture, very delicately wrinkled, in some 

 scarcely visible under 100 diameters, practically smooth, no 

 lirjB. 



S. parvulus Tryon. Apical whorl prominent, decidedly ever- 

 ted and obliquely flattened above. Sculpture, strongly punctate- 

 lirate, the lirse extending well up on the whorl. 



S. pennsylvanicus Walker, Apical whorl rather small, elevated, 

 very much everted and obliquely flattened above, well rounded 

 and constricted by the suture. Apex immersed. Sculpture, 

 strongly spirally punctate on the first half of the apical whorl, 

 running into punctate lirae on the second half, lirate below. 



S. pilsbryanus Walker. Quite variable in the elevation of the 

 apical whorl, which may be prominent, everted, and obliquely 

 flattened above, rounded and constricted by the suture below or 

 blunt, scarcely everted and les^s constricted by the suture. 

 Sculpture, spirally punctate above, obsoletely lirate below. 



