THE SESSILE BARNACLES. 91 



This form is known by several hundred individuals received from 

 II. Loomis with the label Japan and a small lot labelled Yedo Bay. 

 The former grew on small sticks, the base being concave in conse- 

 quence; the Ycdo Bay set lived on stone, and are more strongly 

 ribbed, with flat bases. A small set from Shinagawa Bay, from the 

 Imperial University of Tokyo, Cat. No. 32951, U.S.N.M., has one 

 individual of the typical ribbed form and several having narrower 

 radii and nearly smooth surface, without white ribs, but showing the 

 white septa indistinctly on the purplish parietes. As none of them 

 contain the opercular valves, I do not know whether these smoothish 

 examples represent another subspecies or are a smooth phase of 

 B. a. albicostatus. 



Very rugged examples, the largest with a diameter of 20 mm., 

 were sent from Hirado, province of Hizen, by Mr. Y. Hirase (No. 

 1518, A. N. S. P.). None contain the opercular valves. They grew 

 on stone. It appears that the petricolous individuals of this race are 

 more strongly ribbed than those on wood (pi. 20, fig. 4). 



FIG. 18. BALANUS AMPHITRITE ALBICOSTATUS. a, LABRUM AND b, MANDIBLE. 



A group, without locality, from the North Pacific Exploring Expe- 

 dition, Capt. John Rodgers, United States Navy, consists of strongly 

 ribbed specimens, the largest 19 mm. in diameter, seated on a quartz 

 pebble. The spur of the tergum is decidedly shorter and broader 

 than in the type lot, but the valve has the same elongate shape 

 (pi. 20, fig. 3). 



The figures given by Doctor Kriiger represent different forms of 

 the tergum, such as are found in different colonies, but probably 

 falling within the latitude of variation which must be allowed for a 

 subspecies of Balanus. He figures the labrum with four teeth on 

 each side, but with a hairy margin, as in my preparations. The 

 number of teeth is highly variable in many species of Balanus. 



I referred the specimens of albicostatus at first to B. amphitrite stuts- 

 huri Darwin, described from West Africa, on account of the narrow 

 terga with long, narrow spurs. Several characters of the Japanese 

 form, however, do not agree with Darwin's account, especially the very 

 wide radii, the ribs of the wall, and the absence of epidermis. Dar- 

 win says of his stutsburi that the epidermis is persistent and the 

 radii veiy narrow, and he does not mention any ribs. No other 



