140 THE NAUTILUS. 



aperture of the male is larger than that of the female. This is true 

 also in Nautilus pompilius. 1 



The average columella angle CDE is for males 37.4 and for 

 females 40.4. The columella angle of the females is larger than 

 that of the males. This is characteristic, and it is possible to sepa- 

 rate the males from the females in a large series at a glance with 

 very few errors. One male, however, showed the female angle and 

 one female the male angle. 



The results of these observations indicate that the relation of the 

 variety alatus to the type is not of sexual character, that the aperture 

 of the male may be a trifle wider than that of the female, but the 

 columella angle is a true case of sexual dimorphism. 



A NEW SPICIES OF SOMATOGYRUS FROM SOUTH ALABAMA. 



BY T. H. ALDRICH. 



SOMATOGYRUS WALKERIANUS n. sp. 



Shell small, globose, rather solid, smooth, color greenish-yellow. 

 Spire short, obtuse. The nucleus is obliquely placed, and projects 

 markedly beyond the outline of the spire on the left side. Whorls 

 about four, suture impressed. Body whorl large, slightly shouldered ; 



outer lip slightly expanded. Inner lip thick- 

 ened and rounding below into a rather nar- 

 row and deep groove, which runs up into the 

 slightly perforate umbilicus. Aperture rather 

 pointed above and rounded at the base. Alt. 

 4.25 ; diam. 4 mm. 



LOCALITY. Conecut River, Escambia 

 Co., Ala., twenty miles east of Brewton, 

 living on limestone rocks, rather common. 



REMARKS This shell resembles a small 



_S. subylobosus Say, but is not so strongly shouldered, has a much 

 lower spire, and also the groove behind the pillar lip. Examples in 

 cabinets of A. A. Hinkley and Bryant Walker. Type in my collection. 



1 Bather, 1895, Natural Science, Vol. VI., p. 411. 



