274 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



1870. Diadema californica VAN BENEDEN, Bull, cle 1'Acad. Roy. des Sci. 



des Lettres, et des Beaux-Arts de Belgique, ser. 2, vol. 29, p. 355. No 



description. 

 1874. Coronula diadema Linnaeus, SCAMMON, The Marine Mammals of the 



Northwest Coast of North America, p. 47, pi. 10, fig. 5. 

 1897. Corointlrt diadema, Linimms, WKLTNER, A^erzeichnis, Archiv fiir Natur- 



geschichte, vol. 1, p. 254 (distribution). 

 1900. Coronula diadema Linnseus, WELTNER, Fauna Arctica, vol. 1, p. 302 



(distribution). 

 1903. Coronula diadema Linnseus, STEAD, Proc. Linn. Soc. New South 



Wales, vol. 28, p. 944 (on Balamoptera, off Cavalli I., N. Z.). 



The barnacle is crown-shaped, or formed like a short cask, having 

 convex ribs, crossed by narrow, minutely beaded rugae, the opposed 

 lateral edges of the ribs not crenated. Radii very broad, and seen to 

 be very much thinner than the compartments, leaving a large space 

 filled by branches of the ovary between the radii and alie, visible 

 only when the compartments are separated. Orifice very much larger 

 than the basal opening. Terga wanting, or rarely present as minute 

 vestiges. 



Diameter, 86 mm.; height, 67 mm (Tonga Island). 



Diameter, 75 mm.; height, 59 mm. (Monterey, California). 



Diameter, 63 mm.; height, 31 mm. (Unalaska). 



Diameter, 44 mm.; height, 36 mm. (Unalaska). 



Diameter, 57 mm.; height, 36 mm. (Bering Sea). 



The lamellar parietal folds or ribs branch much less freely than in 

 C. complanata. Individuals up to 45 mm. in diameter and evidently 

 adult sometimes have all of the ribs simple, though usually some are 

 forked. The branches appear first on the rostral sides of the sutures; 

 they are not symmetrically developed on both sides of the sutures, as 

 in C. complanata; nor are the branches arranged symmetrically on 

 the two sides of the barnacle. As a general rule, the more spreading 

 individuals have more branches, thus keeping the buttresses evenly 

 spaced at the periphery. 



The elaborately denticulated radii (pi. 65, fig. 3), are much wider 

 than in C. regince, but they leave a far larger cavity than in C. com- 

 planata. 



Only a small part of the total height of the barnacle is embedded 

 in the skin of the whale. They are often seated upon it about as 

 close as they can stand. One piece of dried whale skin in the United 

 States National Museum, 26 inches long and averaging nearly 5 

 inches wide, supports 118 individual Coronulas of all sizes. 



This is the common w T hale-barnacle of the Northern Hemisphere. 

 It is the " whale louse " of the humpback whales, Megaptera. I have 

 found no record of it from other genera of whales. In the Arctic 

 and Atlantic I have seen specimens from Spitzbergen and Disco 

 south to St. Bartholomew, but it is certainly much less abundant 

 southward. 



