340 Quarterly Journal of Conchology. 



mangroves, where the water is in a great measure fresh, while at 

 Havannah and Colon, when it lives on stakes in water but slightly 

 brackish, it is thinner and smaller and also darker colored. Again 

 the specimens of L. intermedia on stakes at the mouth of the 

 Lorenzo Marques River, Delagoa Bay, are much smaller, darker, 

 and more fragile than those living on grass a few hundred yards 

 away. 



I have sometimes thought the explanation of this might be 

 that those living furthest from the influence of the sea get their 

 salt water only at high spring tides, and are therefore exposed to 

 to greater physical changes than the others dwelling by water in 

 direct communication with the sea. And yet if such were the 

 case, one would expect a coarseness and irregularity in the growth 

 of the former which does not occur. I must therefore be content 

 with recording the results of observation. 



Jan. 4th, 1S78. 



ABNORMAL FORM OF 

 CYLINDRELLA RAVENI, Bland. 



By J. S. Gibbons, M.B. 



Among some specimens of the above species collected on the 

 Island of Curasao, I found a very curious monstrosity — the shell 

 (empty when I picked it up) possessing two apertures placed almost 

 back to back — a kind of MoUuscan " Two-headed Nightingale." 



Originally the shell was undoubtedly an ordinary form, but 

 for some reason or other it has formed a second aperture, about 

 one-third of a volution nearer the apex, the canal of the portion 

 of whorl beyond being obliterated by the columellar side of the 

 new orifice. 



