CIRRIPEDES. MOLLUSCA. ANATIPA. 19 



is in all cases the true explanation, I am not disposed to admit. 

 The largest specimens I have seen were found in a protected 

 situation, under a bridge on the Dorchester turnpike road, and they 

 were so situated as to have full scope for growth in any direction. 

 They were often solitary, and an examination of the space 

 around them forbade the suspicion that they had ever been group- 

 ed. Under the wharves at Provincetown, I have noticed them so 

 crowded as to justify the explanation. Certain it is, however, that 

 the opercular valves, the most important and most constant por- 

 tions, differ in no respect from the depressed conical specimens. 

 All the elongated specimens of our coast have the valves of 

 B. ovuldris. The exterior of the shell is the same also, if we 

 make allowance for the peculiarity of form. We should, there- 

 fore, consider it as an accidental, or rapidly developed, form of 

 some other species. 



ft PEDUNCULATA. Shells pedunculated. 



GENUS ANiTIFA, LAMARCK. 



Shell sub-triangular, compressed, composed of five unequal valves 

 united by cartilage, and seated on a fleshy stalk. 



The shells of this genus are the true barnacles. They do not 

 seem to have a fixed abode anywhere on our coast ; yet they are 

 at all times found among us, either in the character of visiters or 

 emigrants. The shells vary so much with age, that it is not 

 always easy to define the limits of species, or to refer a shell to 

 its true species. More species exist in books than in nature. 

 The animal, when seen alive, in most cases, removes all uncertain- 

 ty. These shells, though everywhere common, seem to be re- 

 garded everywhere as strangers. They are Jews among other 

 shells. Hence they seem to have been but little studied. 



ANATIFA L-EVIS. 



Shell slightly wrinkled by the lines of growth, crossed by very 

 faint, radiating lines ; valve at the back broad, flat, and smooth ; 

 cartilages and stalk at base of shell orange ; animal light-colored. 



WOOD-CUT, (seep. 11.) 

 State Coll., No. 248. Soc. Cab., No. 2083. 



Lepas anatifera, LIN. ; Syst., 1109. CHEMN. ; Conch., viii. 340, t. 100, f. 853. 

 PENNANT ; Brit. ZooL, pi. 38, f. 9. ELLIS ; Phil. Trans. 1758, vol. 50, pi. 34, 



