150 LITTORINID^}. 



Here perhaps is an explanation of some of the differences 

 in allied forms ? Can, for instance, my Singapore specimens 

 catalogued as L. pallescens var. erronea, and those as L. arbori- 

 cola var. pJiilippiana, be the different sexes of one species ? 



Long. 16, diam. 9 1 3 - mil. [Generally a little smaller.] 



The differences from the typical form are probably due to 

 my var. delicatula living in slightly brackish water ? Reeve's 

 L. tennis from the Philippines seems to be an allied form ? 



20 Port Canning and False Point ; coll. Colonel G. B. Mainwaring, 

 Dr. F. Stoliczka, J. Wood-Mason and G. Nevill, Esqrs. 



Of equally fragile texture, but easily distinguished from the 

 female form by the less produced spire, even less developed 

 keel at periphery, and especially by the conspicuously distended 

 aperture and rounded columellar margin at base ; several speci- 

 mens have one or two varices behind the peristome, which is 

 occasionally " subduplex." The coloration is, if possible, 

 even more beautiful and variable ! Long. 14, diam. 8^ mil. 

 Gibbons, Q. J. Con. 1878, p. 339, states that specimens of Lit. 

 intermedia and angulifera become less solid as the water in 

 which they live is less salt ; I am not sure that this applies to 

 the form under consideration as immediately associated with 

 my var. delicatula, may be found normally solid Lit. inter- 

 media and the very thick-shelled Lit. melanostoma. 



var. sub intermedia, nov. 

 10 Port Canning and False Point; coll. Colonel G. B. Mainwaring. 



Long. 15J, diam. 9 mil. 



Most remarkable and interesting specimens, combining many 

 of the characters of L. intermedia, Phil., with those of L. 

 conica. Can they be a hybrid race ? 



The above are what I take to be the ? form. 



8 Port Canning ; coll. Colonel G. B. Mainwaring. 

 These are doubtless males. 



47. Littorina albicans. 



Littorina albicans, Metcalfe, P. Zool. 8., 1852, ftorneo. 

 3 Loc. ? ; ex c. Dr. F. Stoliczka. 



