NO. 1700. O^ THE BARNACLES OF PERU—PILSBRY. 65 



BALANUS TINTINNABULUM (Linn«us). 



Plate 16, flg. 3; plate IS, figs. 5-S. 



175S. Lepas tintinnabulnm Linn^us, Syst. Nat., 10th Ed., p. 668. 

 1854. Balanus tintinuabulum var. communis Darwin, Monograph on the 

 Cinipedia, Balauidae, p. 195, pi. 1, figs, a, b. 



Localities. — Bay of Sechura, about midway between Bayovar and 

 Matacaballa, 5 to 6 fathoms, R. E. Coker, April 10, 1907. Pacasmayo, 

 from a chain on the pier, Dr. W. H. Jones, October 9, 1881. 



The barnacle varies from cylindric, with the orific3 as large as the 

 base, to conic, volcano shaped. The height is about equal to the 

 carino-rostral length, or sometimes is greater, in which case the basis 

 forms part of the side walls. The largest Peruvian example seen 

 measures 5 cm. high and long. Color varying from crimson to dull 

 purple. Orifice longer than wide, more or less distinctly hexagonal. 

 The parietes are not ribbed. The wide, conspicuous, transversely 

 striate radii are level at the orifice. The sheath is glossy and nearly 

 smooth, and the plates are smooth or weakly ribbed below it (pi. 16. 

 fig. 3). 



The tergum is irregularly trapezoidal, the basal and basi-tergal 

 sides about equal. It has a conspicuous sculpture of concentric lam- 

 ellar ridges, joining by pairs at the occludent margin, and in the in- 

 tervals fine stria? radiate from the apex. The plate is bent along a 

 longitudinal line of flexure, the tergal third standing at an angle of 

 about 15° with the rest of the surface. The articular furrow is very 

 deep and narrow, the articular ridge high, usually overhanging at 

 its lower end. Adductor ridge high, overhanging toward the tergal 

 side (figs. 6, 8). 



The tergum is triangular, its spur long and separated from the 

 scutal angle by fully double its width. The longitudinal furrow is 

 usually reduced to an impressed line by the infolding of its edges. 

 The external sculpture is otherwise like that of the scutum. Inside 

 there is a wide and open articular groove, a strong articular ridge, 

 and a stout rib running to the spur. Crests for the insertion of the 

 depressor muscle are weak or wanting (figs. 5, 7). 



This is a common barnacle in all warm seas, probably derived from 

 an oriental center. It is one of the most abundant forms carried on 

 ship bottoms. Whether it reached the west coast of South America 

 by natural means, or was carried there by commerce has not been 

 ascertained. If it proves to be wanting in pleistocene or pliocene 

 deposits of the west coast, the theory of recent introduction may 

 safely be held. 



The Peruvian examples seen all belong to the typical form of B. 

 tintinnahulum, which was called var. communis by Darwin. 

 Proc.N.M.vol.37— 09 5 



