146 THE VOYAGE OF E.M.S. CHALLENGER. 



this new section of the minis. I only wish to add here that one of the peculiarities of 

 the new section is thai both species are representatives of the deep-water fauna, one being 

 found at a depth of 150 fathoms, the other of even 516 fathoms, and that some of the 

 peculiarities of their structure (of the compartments at least) must be regarded as stand- 

 ing in near relation to their living at so considerable a depth. Balanus crenatus, 

 Brucr., according to Darwin, lives at a depth down to 50 fathoms; Balanus porcatus, 

 da Costa, was dredged during one of the cruises of the Dutch schooner " "Willeni Barents " 

 (Barents Sea), at a depth of 140 fathoms; the Challenger took another Balanus (which 

 I consider as new to science, and for which I propose the name of Balanus tenuis) in the 

 Philippine Archipelago, at a depth of 300 fathoms. In this latter species, probably, as 

 well as in the two preceding ones, we have littoral forms in the sense of A. Agassiz, — 

 forms extending from the shore down to 180 fathoms. On the contrary, Balanus corolli- 

 formis might be considered as a deep-sea species, the upward limit of whose distribution 

 rises as high as 180 fathoms. Of course future dredgings will have to show whether this 

 suggestion is right or wrong. 



As the number of species in this genus which I know from personal investigation is 

 small in comparison with those which I have never seen, I have not been able to 

 compose a synopsis for the determination of the species, as was given for the other 

 genera of the group represented in the Challenger collections. 



The sections into which the genus is now divided are : — 



Section A. Parietes, and basis, and radii permeated by pores. Eight species 

 (no new species). 



B. Parietes and basis sometimes permeated by pores, sometimes not ; 



radii not permeated by pores ; shell elongated in its rostro- 

 carinal axis ; basis boat-shaped, attached to Gorgonke and 

 MilleporcB. Five species (no new ones). 



C. Parietes and basis permeated by pores. Radii not permeated by 



pores. Thirteen sj3,ecies (tw r o new ones, Balanus armatus, 

 F. Midler, and Balanus socialis, n. sp.). 



D. Parietes permeated by pores. Basis and radii not permeated by pores. 



Five species (one new, Balanus rostratus, n. sp.). 



E. Basis membranous. Three species (no new ones). 



F. Parietes and radii not permeated by pores ; basis sometimes per- 



meated by pores, sometimes not, and sometimes excessively thin 



