140 



BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



Carinorostral diameter, 31 mm.; height 2G mm. (Tokyo Harbor). 

 By the shape and sculpture of the opercular valves, the wholly solid 

 basis, the square tubes of the parietes, and the development of acces- 

 sory ribs on the inside, betAveen those corresponding to septa, this 

 species is extremely similar to B. balanus; but it differs in the im- 

 portant character of having transverse septa in the parietal tubes. 

 In very long series of B balanus, examined from all parts of its range, 

 there are never an}^ transverse septa, and near the apices of the parie- 

 tes the tubes become filled up solidly. There are also some differences 

 in the opercular valves, as noted under B. balanus. The mouth parts 



could not be distinguished 

 from those of B. lalanus. 

 The cirri of the Bering Sea 

 races have more spines than 

 Atlantic/?. balanus; Bering 

 Sea specimens of balanus, 

 however, have as many. 

 The penis is much longer in 

 B. rostratus. 



Originally described from 

 quite young specimens col- 

 lected by the Challenger, 

 this species has been found 

 to reach about the size of 

 B. balanus. While the typi- 

 cal form is only known from 

 a few localities between Kobe and Tokyo Bay, it will probably turn 

 out to have a much wider range northward, continuous with the range 

 of the following race. 



Like B. Ixtlanus, it usually grows on shells. It is often overgrown 

 with Serpula, the young of its own kind, and in one case with Balmnm 

 trigonus. 



The barnacle recorded from Japan as B. crenatus by Doctor Kriiger 

 agrees with some forms of rostratus in the details figured, but as 

 nothing is said of the radii or cirri, I clare not make a positive iden- 

 tification. It is certainly not B. crenatus. 



Plate 30, figure 1, is from a specimen in the museum of the Acad- 

 emy of Natural Science, Philadelphia, from Tokyo Harbor. A lot 

 of the typical form in United States National Museum from H. 

 Loomis is labeled Japan, without exact locality (pi. 3G, figs. 2, 2a). 



The large development of rostratus forms in the north, where other 

 related species exist, seems to indicate that B. r. heteropus and typical 

 B. rostratus are peripheral southern forms derived from the north. 

 No related species are found farther south. 



Fie. 30. SCUTA OF a, BAT, ANUS ROSTRATOS, JAPAN, 



No. 1814, AND ft, H. R. APERTUS, TOPOFP STRAIT, 

 AT, ASK A. 



