150 THE VOYAGE OF H.M.S. CHALLENGER. 



Balanus Icevis, Bruguiere (PL VII. figs. 2, 3). 



Balanm Icevis, Bruguifere, Enoyclop. M<5tli. (1789), pi. clxiv. fig. 1. 

 Balanm Icevis, Darwin, Balauidse, 1854, p. 227. 



This species seems to be peculiar to the straits of Magellan; it occurs also at the west 

 coast of South America, and even at the coast of California, but then the species has 

 slightly altered ; its shell is not covered with membrane, the orifice is slightly toothed, 

 and it Las two furrows on the scutum, whereas the Magellan specimens have only one, 

 Darwin, therefore, considers the form that occurs at the coast of Chili, Peru, and 

 California, a variety. 



The Challenger collected numerous specimens, forming together globular masses. 

 They are covered by dirty yellowish-brown membrane, and belong doubtless to the same 

 form which was named by Bruguiere, and afterwards elaborately described by Darwin. 

 To his description I do not wish to add anything. I have figured a small globular mass, 

 and a top view of the orifice, which in most specimens is strikingly toothed. The scutum 

 has only one longitudinal furrow. 



These specimens were taken in the straits of Magellan, at Station 312, January 13. 

 1876 ; lat. 53° 38' S., long. 70° 56' W. ; depth, 10 to 15 fathoms ; bottom, mud. 



Balanus socialis, n. sp. (PL XIII. figs. 23-28). 



Shell not covered by a distinct membrane ; orifice relatively large, and not deeply 

 toothed ; radii extremely narrow. Tergum with a broad and short spur, and an 

 extremely long basal margin. 



In this species the walls as well as the basis are permeated by pores ; the radii, 

 however, are not permeated ; whence it belongs with the preceding species to the section 

 C of Darwin. It has a tergum of highly characteristic form (PL XIII. figs. 25 and 27), 

 and it is represented by a single group of specimens attached to a very curious object, of a 

 nature quite unknown to me. The shape of this object may be judged from fig. 23 on 

 PL XIII. Its colour is black as long as it is in alcohol ; when dry it is dirty brown 

 coloured. It is hollow ; it has a membranous wall within the outer thick wall. It is 

 empty ; yet I think I may conclude from the histological structure of the outer wall that 

 it is either a fruit or the stone of a fruit. 



About a dozen specimens are attached to one side of this object, which is fiat and 

 slightly hollowed out. They are rather small ; the greatest diameter of the base of the 

 largest specimen does not measure quite 5 mm. ; their height is only half that length. The 

 form of the shell is deep-conical ; the orifice is slightly toothed and comparatively large ; 

 when closed the opercular valves are nearly horizontal, parallel at least to the surface of 



