138 THE NAUTILUS. 



shrubs, grass and weeds. On the sandy part I found immense num- 

 bers of dead shells of Cerion incanum and a diligent search revealed 

 a fe.w living examples on grass close to or even on the sand. As the 

 weather for the past few days had been unusually cold, I thought it 

 possible that it might be buried in the sand, and digging around the 

 roots of bunches of grass I unearthed tlie spe>^ies alive by thousands. 

 In some cases a double liandful would be buried around a small 

 bunch of grass. Many of the specimens had a thin, almost transpar- 

 ent epiphragm at the aperture, while occasionally it was deeper 

 seated, thicker and white. 



The apex is rather conical, the apical whorls are corneous, while the 

 last whorl has strong irregular wide-spaced riblets and a dark base, 

 often outlined by a revolving bluish stripe. The body of the shell 

 is a uniform bluish-white, and occasionally a specimen has the base of 

 nearly the same color. In a somewhat wide experience of collecting 

 this species, I have never seen it so abundant. Associated with it were a 

 few Polygyra carpenteriana and rarely a Glandi7ia truncata minor. 



In the Manual of Conchology, Vol. xiv. p. 215, Pilsbry states 

 that Mr. S. N. Rhoads found five specimens of the Cerion incanum 

 on Virginia Key, but that he thought they had probably been drifted 

 there, and Pilsbry believes this key to be the extreme northeastern 

 limit of the species. *' Baker's Haulover " is eight or nine miles 

 north of the extreme northern end of Virginia Key and is on the 

 mainland. I followed up the beach from the " Haulover " for a half 

 mile perhaps, but there seemed to be no diminution in the numbers of 

 specimens at the farthest point reached. 



Lemon City, Florida. 

 Jan. 29, '05. 



SEXUAL DIMORPHISM IN STROMBUS PUGILIS LINNE. 



BY HAROLD SELLERS COLTON. 



Sexual dimorphism does not seem to be common among the Gaster- 

 opoda. It can occur only in the sub-class Streptoneura, in which the 

 sexes are separate. Cases are seldom reported. When they are, 

 they are hidden amid a mass of facts in some large work. I find 

 that sexual dimorphism has been noticed in Margarita helicina^ and 



' Dwight Blanej-, Proc. Boston Society of Nat. Hist., Vol. XXXII., No. 2, p. 

 38, 1904. 



