THE SESSILE BARNACLES. Ill 



Type-locality. Okinose bank, Sagarni Bay, Japan. 



Numerous examples from three Albatross stations seem referable 

 to this species, agreeing well with the description, except in having 

 the lower teeth of the mandible blunt. 



D. 5134. Sulu Archipelago, near Balukbaluk Island, 25 fathoms. 



D. 5135. Sulu Archipelago, vicinity of Jolo, 161 fathoms. 



D. 5146. Sulu Archipelago, vicinity of Siasi, 24 fathoms. 



BALANUS TRIGONUS Darwin. 

 Plate 26, figs. 1 to 13e. 



1854. Balanus trigonus DARWIN, Monograph, etc., p. 223, pi. 3, figs. 7a-7/("Java; 

 East Indian Archipelago; Peru; West Colombia; California; Sydney; New 

 Zealand"). 



1867. Balanus armatus MULLER, Archiv fur Naturgeschichte, Jahrg. 1867, vol. 1, 

 pp. 329-356, pi. 7, figs. 1-21, 23-28; pi. 8, figs. 44, 46-48; pi. 9, fig. 56. 



1868. Balanus armatus MULLER, Ann. Mag. Nat. Hist., vol. 1, p. 392. 

 1897. Balanus trigonus Darwin, WELTNER, Verzeichnis, p. 262. 



1911. Balanus trigonus Darwin, KRUGER, Beitrage zur Cirripedienfauna Ostasiens, 

 in Abh. Math.-Phys. Klasseder K. Bayer. Akad. Wissensch., vol. 2, Suppl.- 

 Band, p. 49, figs. 98-100, pi. 1, fig. 6; pi. 3, fig. 33. 



Type. British Museum. 



Distribution. Pacific, from Tokyo Bay, Japan, through the East 

 Indies to Sydney, New South Wales, and New Zealand; Red Sea; 

 West America from Peru to southern California. Atlantic, West In- 

 dies to southern Brazil; Madeira and Azores to South Africa. 1 



According to Darwin, it is described as follows : 



Parietea ribbed, mottled purplish-red; orifice broad, trigonal, hardly toothed. 

 Scutum thick, with from one to six longitudinal rows of little pits. Tergum without a 

 longitudinal furrow, spur truncated, full one-third the width of valve. 



General appearance: Shell conical, generally depressed; orifice broad, triangular, 

 almost equilateral; walls colored or only mottled with purplish-pink, having either 

 irregularly branching, or regular, longitudinal ribs, which are generally white. The 

 radii are pale pink or nearly white; the opercular valves have either their upper 

 parts, or nearly their whole surface, clouded with pinkish-purple. The epidermis is 

 not persistent; the walls are moderately strong. The largest specimen was one inch, 

 but generally full-grown specimens are about half an inch in basal diameter. 



The opercular valves have their lower growth-ridges minutely 

 fringed with bristles when unworn. The membrane lining them is 

 dark purple. When cleaned both valves are in part of a pink color 

 internally. 



The scutum has prominent, narrow growth-ridges which cross 

 several deep longitudinal furrows, producing rows of small, deep pits. 

 There may be from two to six such rows in San Diego individuals of 

 one group. Very rarely there are individuals without pits, according 

 to Darwin. The articular ridge is rather long; articular furrow deep 



1 The locality "Delaware," given by Weltner (Verzeichnis, p. 262), could refer only to imported speci- 

 mens, as B. trigonus is certainly not found living there. 



