BARNACLES 255 



incrusted with barnacles, and holds the ear near, the closing of 

 the many doors may be distinctly heard. 



The development of Balanus from the larval stage, as also 

 the anatomy of the adult, is similar to that of Lepas. When 

 covered with water and unmolested, there may be seen over a bed 

 of barnacles thousands of tiny fringed feet waving to and fro. 

 The motions look like gestures; they are perfectly regular and 

 rapid, numbering eighty to a hundred a minute. The shell 

 covering formed by barnacles on piles of wharves and bridges is 

 said to be a protective agent; otherwise the barnacles seem to 

 have no economic value in nature, as, unlike other animals, they 

 do not serve, except in very small measure, as food to other 

 classes. The tautog and perhaps some other fishes feed partly 

 upon them. They are sometimes an obstacle to oyster-culture, as 

 they fasten upon the objects intended for oyster embryos, and, 

 growing faster than the latter, soon crowd them off. One species, 

 Coronula diadema, fastens to the skin of whales. It attains the 

 size of two inches in diameter. The shell is half an inch thick 

 and full of cavities, into which the skin of the whale is drawn, 

 giving the barnacle a secure hold. (Plate LIX.) 



B. balanoideft (Stimp.), B. ovularis (Gould), the rock-barnacle. 

 This is perhaps the most conspicuous of the barnacles. It inhabits the 

 whole northern Atlantic coast, and is so abundant that it not only 

 whitens the rocks with a complete incrustation of shells, tut the 

 animals are so crowded that many of them lose their normal shapes and 

 become greatly elongated. When the rocks are covered with water 

 they seem alive, on account of the thousands of waving tentacles. This 

 species also incrusts woodwork between tide-marks. 



The shell is small, white, and variable in shape ; sometimes its height 

 is less than the diameter of its base ; again the height is several times 

 greater and the summit broader than the base. In its early stages the 

 valves are smooth, but later the base is scalloped by four or five grooves. 

 The summit of the plates is even and blunt. The aperture is diamond- 

 shaped. Two valves of the operculum are pointed at the tips ; two 

 are blunt, making a deep notch in the summit. These valves are the 

 distinctive feature by which to recognize this species, which varies so 

 much in outward form ; the species is also distinguished by its mem- 

 branous base, which does not form a solid plate like that of other 

 species. 



B. eburneuSy the ivory barnacle. This species, like B. balanoides, is a 

 very common barnacle, and is found on all kinds of submerged wood- 

 work, whether fixed or floating. It is also found on the carapace of 



