NO. 1700. ON THE BARNACLED OF PERU—PILSBRY. 69 



This barnacle grows on the shell of the gastropod Concholepas 

 peindnana Lamarck, wholly covering the outer surface, as showni in 

 pi. 17, showing dorsal and ventral aspects of two shells so over- 

 grown. The barnacle profits no doubt by riding a gastropod, but 

 whether the Concholepas benefits hy the protection afforded is some- 

 what in doubt. It is distinguished from B. Iwms Bruguiere, of more 

 southern waters, chiefly by the diminished size and absence of cuticle 

 over the outer walls. B. I. n'ttkhis is usually quite nude, but occa- 

 sionally retains some of the cuticle around the base of the walls. 

 The furrows of the scutum are characteristic and present in very 

 many individuals I have examined, but Darwin mentions finding in- 

 dividuals without the grooves. 



BALANUS PERUVIANUS, new species. 



Plate 19, figs. l-l. 



Locality. — Salt creeks at La Palasada, near Tumbez, growing on 

 mangroves. 



Cotijpes.—CAit. Nos. 38691 and 38G92, U.S.N.M. 



A species of Darwin's Section 1). The parietes are ])ermeated by 

 pores near the base ; the radii and base are not porous. 



General form conic, with flat or concave base and rather small 

 aperture; dirty purplish white or dull purple; very solid and strong. 

 The parietes are smoothish, without ribs, and only minutely rough- 

 ened ; radii narrow, their summits sloping 

 steeply; summits of the alse also steeply 

 sloping. The aperture is pentagonal, with 

 a strongly notched margin. The sheath is 

 horizontally regularly ribbed, each rib bear- 

 ing a row of short bristles pointing upward. 

 Below the sheath the surface is strongly 

 ribbed vertically. fi'- i.— bal.\nu.s peruvianus, 



The scutum is triangular, nearly half as lateral view. 



wide as long. It is white inside, dirty whitish outside, suffused with 

 dull purple near the apex, and with a narrow streak of the same near 

 the tergal margin. The basal margin is slightly curved, and the baso- 

 tergal angle is rounded off. The surface is sculptured with flat, 

 slightly overhanging concentric ribs parted by narrower intervals. 

 There are uo radial striae. Inside there is a strong and very high 

 articular ridge, a much lower adductor ridge joining it, and rapidly 

 diminishing downward. Articular furrow deep. The cavity of the 

 adductor muscle is very deep (figs. 3, 4). 



The tergum is bicolored, the scutal half white, carinal half dull 

 purple. The spur is short, w^de, and obliquely truncate at the end. 

 Its width is contained about two and a half times in the length of 



