272 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



ciilar vah^es much smaller than the orifice of the shell, the terga ves- 

 tigial or absent, scuta connected by a chitinous ligament. Oral bor- 

 ders of the opercular integument projecting hood-like. 



Type — Coronula diadema (Linnffius). 



Distribution — All seas ; living on whales. 



The whale barnacles are admirably adapted to resist the impacts 

 incident to their station, the radially symmetrical and buttressed wall 

 being ideally constructed for strength. The morphology' of Coronula 

 has been discussed bj^ Darwin with characteristic insight and clarity. 

 It will suffice here to direct attention to the fact that the partitions 

 seen in the base are not homologous with the parietal septa of Balanus, 

 but with external parietal ribs. These ril)S are narrow, much length- 

 ened, and looped T-like at the ends, thus forming an external Avail, 

 analogous to the fly of a tent. The cells partitioned off by the ribs, 

 and filled by the skin of the whale, are therefore external to the 

 barnacle, though inclosed except on the bottom by processes of its 

 walls. 



Further features of note are the minute longitudinal stride of the 

 parietes, producing beads where they cross circular ripples or 

 wrinkles; a structure common also to TuhicineUa and Platylepas. 

 The hood-like oral border of the sack, shown in plate 65, figure 4, 

 occurs also in Xenohalanus^ TuhicineUa, and Cryptolepas. 



C. diadema lives only slightly embedded in the skin, and it very 

 frequently affords support to the stalked l^arnacle, C oncJiod erma ailri- 

 tuTYh. C. reginm is about one- fourth or more covered by the skin, or in 

 other words, the edges of the barnacle cut into and embed themselves 

 in the skin of the host. Coronulte are disliked by whalers because they 

 dull the knives used in " cutting in." 



C. diadema is a common and long known barnacle, but C. compla- 

 nata, while Imown since 1705 or earlier, is comparatively rare in col- 

 lections, and we have little information as to its distribution, and none 

 upon its station or soft anatomy. C. f'efjince has been the rarest 

 species, as no author except Darwin seems to have seen it ; but we now 

 know that its station is on the lip of the humpback whale, in both the 

 North Atlantic and the North Pacific Oceans. It is probably not very 

 rare, though being inconspicuous it has not often been collected. 



KEY TO SPECIES OF CORONULA. 



a\ Botly-chamber shaped like a teacup, the orifice much larger than the basal 

 opening; slieath running nearly to the base of the inner wall; bi'anchef3 

 of the sutnral ribs not symmetrically arranged, the ribs sometimes with- 

 out branches ; opposed sides of the terminal flanges of the ribs crenulated ; 

 radii less than half the thickness of the compartments, leaving a cavity 

 between radii and alse. Subgenus Coronula. 

 6\ Crown-shaped, elevated, the parietes convex, with cunvex ri))s. 



C. diadema, p. 273. 



