THE SESSILE BARNACLES. 75 



BALANUS PSITTACUS (Molina). 

 Plate 17, figa. 1 to 4; plate 18, figs. 1 to 3. 



1782. Lepas psittacus MOLINA, Saggio sulla storia naturale del Chili. 1 



1818. Balanus tintinnabulum, var. c. RANZANI, Opuscoli Sci., vol. 4, p. 69, pi. 3, 



figs. 1-4. 

 1831. Balanus picos LESSON, Voyage autour du Monde de la Coquille, Zoologie, 



vol. 2, pt. 1, p. 445 (Concepcion, Talcahuano, S. Vincent, Chili). 

 1854. Balanus psittacus DARWIN, Monograph on the Cirripedia, Balanidse, p. 206, 



pi. 2, figs. 3a-d (Arica to Chiloe I., Chili). 



1904. Balanus psittacus Molina, GRUVEL, Nouvelles Archives du Muse'um d'Hist. 

 Nat., se"r. 4, vol. 6, p. 103, fig. 9. 



1905. Balanus psittacus VAYSSIERE, Annales de la Faculty des Sciences de Mar- 

 seille, vol. 15, fasc. 5, p. 161, pi. 1, figs. 1-4 ("Taleahuana," Chili). 



1909. Balanus psittacus (Molina) PILSBRY, Proc. U. S. Nat. 'Mug., vol. 37, p. 66, 

 pi. 16, figs. 1, 4; pi. 18, figs. 1-4. 



Distribution. Strait of Magellan to Pacasmayo, Peru. 



The barnacle is pale pink or sometimes soiled white, conio when 

 young, often becoming subcylindric with age, sometimes very large, 

 with a very long tapering basis. 



The scutum (pi. 17, figs. 3, 4) is trapezoidal, the basitergal corner 

 being cut off, forming an oblique edge parallel to the occludent 

 margin, and about as long as the rest of the base; tergal third of the 

 valve deflected. Sculpture of rather strong growth-ridges crossed by 

 fine but deeply engraved longitudinal strise. Articular furrow nar- 

 row. Articular ridge high and thin, continuous with the high, oblique 

 adductor ridge, which arches over the space between the ridges, 

 leaving a cavity wliicli penetrates nearly to the apex. 



The tergum is very narrow and long, terminating in a long IteaTc of a 

 pink or purplish color. The spur is long, narrow, and less than its 

 own width from the basiscutal angle, usually very close to it. Groove 

 to the spur closed. External sculpture of growth-ridges and radial 

 striae, but both are often very weak. Inside, the articular ridge 

 stands upon that running to the spur. Between this ridge and the 

 carinal border there is a short, narrow, longitudinal ridge; these 

 ridges and an oblong space between them being purple or deep pink. 

 There are no crests for the depressor muscles. 



Compartments. The tubes in the parietes are rather large, not. 

 filled up above, and not transversely septate. The inside below the 

 sheath is ribbed in young, usually becoming smooth in large indi- 

 viduals. The radii are very wide, with level summits, and permeated 

 by unusually large pores. Their distal edges are wide, with rather 

 coarse, branching laminsB, which are deeply denticulate on then- 

 lower sides only. Alse have oblique summits. Laminse of the sutural 

 edges denticulate on the upper side. 



1 See Proc. U. S. Nat. Mus., vol. 37, p. 6(3, footnote a, for some account of the various editions of the 

 Abbe Molina's Natural History of Chile. 



