THE SESSILE BARNACLES. 219 



o a . Color purplish or white ; scutum with crests for the lateral depressor muscle. 

 &\ Basal and internal edges of parietes roughened by irregular points and 

 ridges. Tergiim very narrow, w.lh a rather long, pointed spur. 



c 1 . Exterior smooth B. jlownliis Darwin. 



c 2 . Exterior with sharp longitudinal ribs B. f. sordidus Darwin. 



& 2 . Externally covered with an orange epidermis. Lower internal surface 

 of parietes subregularly ribbed. Tergum with a short spur, obliquely 

 truncate distally B. vestitus Darwin. 



BALANUS IMPERATOR Darwin. 



1854. BaJanus imperator DARWIN, Monograph, p. 288, pi. 8, figs. 4o-4c. 



Type. British Museum. 



Distribution. Eastern Australia, Sydney, New South Wales, to 

 Moreton Bay, Queensland (Darwin). 



A very distinct species by its beautiful dark violet or dusky- violet 

 interior and the peculiar base of the wall, formed of a mass of de- 

 pending points, and by the long third pair of cirri. 



The United States National Museum possesses specimens without 

 locality. 



BALANUS VESTITUS Darwin. 



1854. Balaniis vestitus DARWIN, Monograph, p. 286, pi. 8, figs. 3a-3&. 



Type. British Museum. 



Distribution. New Zealand, New South Wales (Darwin). 

 Dry specimens are in the United States National Museum from the 

 Bay of Islands, New Zealand. 



BALANUS FLOSCULUS Darwin. 

 Plate 51, Figs. l-l/. 



1854. Salami s flosculus DARWIN, Monograph, p. 290, pi. 8, figs. 5a, 5c-5/, 

 with var. sordidus DARWIN, Monograph, p. 290, pi. 8, fig. 5&. 



Type. British Museum. 



Distribution: Peru and Chili; var. sordidus from Tierra del 

 Fuego; attached to littoral shells, wood, and rock (Darwin). 



The specimens in hand from Chili, on the gastropod Concholepas, 

 are small, up to diameter 8.5 mm., altitude 3.5 to 4 mm. Form con- 

 vexly conic, with small aperture, its margins not toothed. The walls 

 are thick, solid, externally with strongly, irregularly ribbed parietes ; 

 radii very narrow. Internal basal edges rough, with coarse, irregu- 

 lar points and ridges, extending nearly up to the sheath, behind which 

 there are small cavities (pi. 51, fig. 1&, carina). The basis is cal- 

 careous and usually so excessively thin that it is hardly noticeable. 



The scutum is strongly convex externally, finely marked with 

 growth ridges. Inside salmon tinted, concave, the free apex long. 

 Articular ridge small but rather long. Adductor ridge acute and 

 strongly curved, terminating at the middle of the basal margin. 

 Lateral depressor muscle attached to one or two short crests below 



