568 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



found. Between any tw^o of the shells collected, no matter how 

 divergent in type, a completely intergrading series could be 

 found. 



It is doubtful if these colors and color patterns are of protec- 

 tive value. The shell is enclosed by flaps of the mantle most of 

 the time rendering the coloration invisible. Also all types of 

 color pattern are seen in one locality. Then, too, the animals 

 are in such great numbers that they could hardly escape the 

 observation of their predatory^ enemies, if such they have, by 

 means of their coloration. 



The shells showii as numbers ^b, %b, 19 and 22 are from Port 

 Antonio, probably from the stream in which Professor Andrews 

 found Neritina, a small shaded stream with a dark bottom of 

 vegetable mould. One can readily observe that the shells from 

 the Port Antonio stream are darker than those on the unshaded, 

 light-colored sand beach of the Salt Pond. P'ew of them resem- 

 ble numbers i to 5 or the a shells of the accompanying plate. 

 Most are heavily marked with dark lines, many of the type 

 shown in 8^ being found. As a whole, the shells from the 

 stream average much darker than those from the Salt Pond. 

 Also it is noticeable that the ground color of almost all of these 

 fresh-water shells is yellow, while that of the Salt Pond shells is 



Remembering that it is doubtful if the coloration of these 

 shells is to any considerable extent protective, it is interesting 

 to find that the darker-colored shells are found in the midst of 

 dark-colored surroundings, in a shaded stream, while the lighter- 

 colored shells are from an unshaded beach of light-colored sand. 



Comparison with the collections of Neritina virginca in the 

 United States National Museum and in the Museum of the 

 Philadelphia Academy of Sciences shows that the color of the 

 Jamaica Salt Pond shells averages considerably lighter than that 

 of shells from the ocean, the ground color being a clearer white, 

 and shells of the patterns represented in figures i to 6 and la 

 to 6a being present in larger proportion. 



Few, if any, finer examples of diversity in color and in color 

 pattern are known. The same types of coloration are found in 

 the full grown shells from the ocean. In the absence of breed- 



