182 



BULLETIN" 93, UNITED STATES NATIONAL MUSEUM. 



SEMIBALANUS, new submenus. 



The basis is membranous; parietes porous, or with the pores filled 

 up; 'ulterior not longitudinally ribbed, but usually having small 

 anastomosing wrinkles near the basal edge; rostrum not prolonged 

 downward below the other compartments. No spinules or "teeth" 

 on the cirri. 



Type. Bui an us cariosus. 



I do not regard B. balanoides and B. glandula as transitional be- 

 tween the Balani with solid and those with porous walls. They 

 are porous forms which have filled up the pores more or less com- 

 pletely, in some individuals. While related to the typical group of 

 Balanus^ this subgenus is strongly individualized. The membran- 

 ous basis and the profusely bristly third cirri, without spinules on 

 the outer faces of the segments, are primitive characters, but the 

 closing of the parietal pores in B. balanoides and their multiplica- 

 tion in B. cariosus are relatively more evolved features than the 

 ordinary types of porous wall. 



KEY TO SPECIES. 



Parietes copiously ribbed externally with several rows of unequal pores ; tergum 

 very narrow, with long, narrow spur and a more or less closed external 

 furrow . B. cariosus. 



Parietes coarsely folded or smooth, the pores normal or obsolete ; tergum with 

 short spur and no trace of an external furrow B. balanoiiles. 



BJ^LANUS BAL.ANOIDES (Linnaeus). 

 Plate 44. 



1766. LCIJOS balanoides LINN-^US, Systema Naturae, ed. 12, p. 1108. 



1789. Balanus fislulosus BRUGXTIEKE, Encyclopedic Methodique, p. 166. 



1790. fLepas elongata Gmelin, Syst. Nat, ed. 13, p. 3213. 



1799. Balanus clavatus PULTENEY, Catalogue of the birds, shells, and 



some of the more rare plants of Dorsetshire, p. 25. 

 1818. Balanus palmulatus LAMAKCK, Anim. sans Vert., vol. 5, p. 394. 



