THE NAUTILUS. 



139 



Fig. 1. 



Buccinum undatuin^ by Morse, in Crepidida^ by Conklin, in Rhsoa 

 nculeus^ and Littorina liUorea*' by^JeflFreys, and in Fidgur carica by 

 Burnett Smith.* As far as I can find out, no one has reported it in 

 Strombus pugilis. 



The material was collected to determine if the variety alatus was 

 but a case of sexual dimorphism, and if not was there any such dif- 

 ference. 1 collected most of the individuals after a severe "norther" 

 in the latter part of January which had cast tliem up in moderate 

 numbers on the beach of Sand Key near Clearwater Harbor, Florida. 

 Of those I examined, nineteen were males and nine wei-e females. 



The variety alatus differs from the type in that it lacks the char- 

 acteristic tubercles on the body whorl. Forty-four per cent of the 

 females and twenty-six per cent of the males showed a tendency to 

 be smooth. Of these observations 

 and the ones to follow, the probable 

 error is so very large, on account of 

 the small number of individuals at 

 hand, that only where the differ- 

 ences are pronounced, are the results 

 of value. 



On the material at hand I made 

 thefollowing raeasurements;-(Fig. 1) 

 the length AB, the width CE, the 

 angle at the apex, the columellar 

 angle, and the aperture FG. On 

 account of the ornamentation of the 

 shell, the width CE and the apical 

 angle were found to be so variable 

 as not to be favorable for compar- 

 ison. The ratio of AB to FG was 

 in the case of females larger than in 

 the case of the males. If this be 

 true, and I have too few individuals 

 to be sure of it absolutely, a very interesting feature is shown. The 



'E. S. Morse, 1876, Proc. Boston Society of Nat. Hist., Vol. XVIII. 



2E. G. Conklin, Jour, of Morphology, 1897, Vol. XIII., No. It 



^JefiFreys, British Conchology, Vol. IV., p. 38. 



*'lbid., Vol. III., p. 343. 



^Burnett Smith, 1902, Proc. Acad. Natural Scienceof Phila., Vol.LIV., p. 507. 



