LITTORINA. 47 



yet a little contracted posteriorly, and broadly rounded 

 anteriorly, owing to the thickness of the shell, is small 

 compared to the peristome ; its colouring is either whitish, 

 or tinged with violet, liver colour, or chocolate. The ex- 

 treme length of the peristome is fully two-thirds of the 

 total length of the shell, its breadth decidedly exceeds 

 one-half of the basal diameter. The outer lip is bevelled to 

 an acute edge, is disposed to expand, recedes considerably 

 at the base, is well rounded anteriorly, and is gently arched 

 and much shelving posteriorly. The pillar lip, which is 

 glossy, and shelves much inward, is broad, and less 

 flattened than in most British species of this genus ; it 

 is broadly confluent with the outer lip, being chiefly, and 

 rather suddenly, dilated at the base of the shell, near 

 which its outer or free margin is concave, but becomes 

 straighter as it recedes thence. The margin of the 

 enamel, which surmounts the pillar in adult specimens, 

 is straightish or incurved. A linear indentation for the 

 most part bounds the inner margin of the columella. In 

 immature examples the mouth is narrower, being longi- 

 tudinally oval, and is produced and attenuated anteriorly. 



In aged specimens, the final whorl is apt to become 

 suddenly deflected at its termination, which causes the spire 

 to seem much more elevated, and the length of the shell to 

 become equal to its breadth. 



In the other variety, the body not being so obliquely 

 placed in regard to the lesser volutions, the general shape is 

 much more globose, and the angularity of the final whorl 

 much less conspicuous ; the spire is more raised, and the 

 aperture more oval. The outer lip, too, is generally 

 thinner, and the minute spiral wrinkles more wavy.* 



* The L. Neritiformis of Brown (111. Conch. G. B. p. 17, pi. 10, f. 24), whose 

 description we here transcribe, seems to be a somewhat distorted form of this 



