PLATE XXXVI. 



male and female animals of this kind, the two sexes being isolated or 

 distinct individuals ; they are of an amphibious nature, liviqg in the 

 sea, from whence they ascend occasionally and crawl about the rocks. 



Linnaeus under the Nerita genus comprehends as well the 

 imperforated or non-umbilicated kinds as those which have that 

 perforation. The later continental writers divide these again, retain- 

 ing the name Nerita to those which have no perforation ; those with 

 a perforation are called Natica, by the french authors Natice, after 

 Adanson, Gualtieri, and Favanne. Lamarck has also a genus 

 Neritina, and another Navicella, all which in the Linnaean system are 

 of the Nerita tribe. 



Nerita Polita is by no means an uncommon shell upon the 

 coasts of the Indian Ocean, being found throughout their whole 

 extent from Japan to the Cape of Good of Hope, and as it appears 

 also upon the shores of many islands in the Indian and the Great 

 Southern Ocean. 



Besides being so very abundant in those parts, it may also be 

 observed that no species of the testaceous tribe is more remarkable 

 for the almost endless variety of colours, or the form and disposition 

 of the spots, dots, and lineations, than the individuals of this kind of 

 Nerit. There are, however, some few of its varieties which from 

 being local are far less abundant than the rest, and the shell in par- 

 ticular which we have selected for the most conspicuous object in the 

 annexed plate is one the most important of the number. The pre- 

 vailing colour of the ordinary varieties is olivaceous, in some paler, 

 in others more inclining to blackish ; the charactered marks in general 

 yellowish, triangular or sagittate, and varied with short blackish lines. 



