40 TESTACEA. 



The shell sometimes grows pale, and becomes almost white. 

 Marine ; not common. 



Plate VIII. 



Fig. 3. Trockus ziziphynus, surface. 



4. Under surface of the minimal. 



5. Shell. 



TURBO. 



This is a genus which comprehends numerous species, and seems to 

 be undergoing dismemberment, in common with others of the less re- 

 markable groups, because in a great measure destitute of characters sul- 

 ticiently definite. 



Turbo quadrifasciatus. — Plate "M^II., Figs. 6, 7. 



Length of the shell three lines ; volutes four ; colour brown, with 

 four darker reddish belts. Animal a Limax ; head round, with two long 

 slender active tentacula, m much motion. A black eye at the external 

 base of each ; posterior extremity obtuse. An organ, half the length of a 

 tentaculum, issues from each side of the broadest part of the sole ; colour 

 grey, red, or brown, sometimes greenish, being derived perhaps from the 

 nature of the food. 



Margin of the posterior extremity white, in form of a horse-shoe. 



Feeds on the Laminaria ; spawns in August. 



Plate VIII. 



Fig. 6. Turbo quadrifasciatus : Shell. 

 7. Animal under surface. 



jYote. — There are various other Testacea of much the .preceding clia- 

 racter, but of which the difference is not sufficiently marked to constitute 

 positive distinctions. They are represented in the following Figures. 



