534 



part of the whorls being more conical, and the peculiarity of 

 marking being constant in the former, we think it will always be 

 recognized with facility. In the absence of any real definition of 

 the word species as applied to shells, we should generally be 

 guided in our divisions by the facility with which a specific dis- 

 tinction would be recognized. 

 West Indies, Brazil. 



90. Neriti^a Mertoniana (pi. cxvi. f. 242-216), Recluz, 

 Pro. Zool. Soc, 1843, p. 71. N. Oualanensis, Lesson. N. nebu- 

 lata, Recluz. 



N. testa N. Virginia, simili, sed magis subglobosu,, anfractu 

 ultimo superne subangulato. 



The variety, f. 246, N. Oualanensis, Recluz, is thinner and 

 generally smaller than the other variety; the variety N. nebulata, 

 liecluz (f. 243), is larger, and marked with scales as in N. niclea- 

 gris, but we can only distinguish the three from N. Virginia by 

 one character which they have in common, which is, that they 

 are rather more globose, and have a very faint, rounded angle at 

 the upper part of the whorls. 



Var., f. 246, Oualay, Sandwich Islands, and Port Essington ; 

 f. 242, 4, 5, N. Mertoniana, Island of Negroes ; on stones in a small 

 stream ; var. N. nebulata, ditto. Cuming. 



91. Neritina Listeri (pi. cxvi. f. 249-251), Pfeiffer. 



N. testa N. Virginia et N. reclivatai simili, sed multum magis 

 globosa, spira, plana. 



More globose than N. Virginia and N. reclivata, with the 

 whorls of the spire not at all produced. Some varieties of N. Vir- 

 ginia occur which are almost ecpially globose ; but in these the 

 spire is more produced. 



The large specimen, f. 249, is from Cuba; the other variety 

 is from St. John's river, Nicaragua. 



92. Neiutina meleagris (pi. cxvi. f. 252, 253), Lamarck, 

 Chemn., 124. f. D. L. 



N. testa N. Virginice simili, sed magis globosa, minus obliqua, 

 spira subconica sed minus producta. 



More globose and less oblicpie than N. Virginia; the spire, 

 although conical, much more central, and less produced; the 

 upper part of the last whorl being more elevated, but not so much 



