Nos. 451-452.] 



NERITINA VIRGINEA. 



itself to life in fresh water or to water of greater salinity than 

 that of the ocean, but unable to attain its full size except in the 



The dwarfed forms may fairly be called a varictv, thou-ii their 

 difference from the ocean forms be only one ot size i)i<.l)al)ly 

 directly due to increased or decreased salinity <»t the water in 

 which they live. 



The great diversity in color and in color pattern touiui m 

 Neritina virginea is well known, yet it ma}- he wiutli while to 

 call attention to the completeness of the interi;ra(Hii,i; hrtween 

 any two types, however divergent. 



Color shade. — ^ote first the differences in the - round color 

 of the shells : yellow in sb, iq, and 22 ; white in all the rest. 

 Observe that the colored lines are black in 1,3, 5, 5/--, 6, 6a, 19, 

 20, 22 ;^ purplish in 6b and 11 ; red in "ja; gray in 23; black 

 and red in 2 ; that the major lines are black and the minor lines 

 red in la, 3, 3^?, 4, 4^, and 5^ ; that the major lines are black 

 and the minor lines purple in 4b, 17 and 16. 



Color pattern. — i is marked with a few heavy lines. From 

 I to 6 these major lines become broken ui) into small \'-shape(l 

 loops. In the shells a acces.sory minor lines are added. In the 

 shells b these are more numerous. 



Series 9 to 14 shows diversity in the pattern near the apex 

 of the coil : 9 has a few slightly larger white dots near the coil, 

 10 has larger dots here, 11 has them very large ; in 12 they 

 have united to form a continuous white band ; in 13 and 14 this 

 band is wider. 



Series 15 to 24 shows diversity in the character of the et|uato- 

 rial light band. In 15 and 16 only the min.)r lines are inter- 

 rupted or faint along the equator of the shell ; in 17 the major 

 lines also are interrupted ; in 18 the band is almost clear white ; 

 19 and 20 show narrower bands ; in 21, 23 and 24 the equato- 

 rial band is sho%vn by a difference of color in and under the pat- 

 tern ; in 22 the equatorial line is faintly indicated in the pattern 

 itself, being bordered above and below by large, heavy, black 



The shells figured are but a few selected from the large num- 

 ber collected. Other types of color and of color pattern were 



