440 L. A. BORRADAILE. 



VII. THE BARNACLES (CIRRIPEDIA). 



Seeing that the Barnacles are sessile animals, and need to attach themselves to a firm 

 holdfast, it might be expected that they would be numerous and characteristic inhabitants 

 of coral reefs, which give so many opportunities of settlement on fixed bodies, under con- 

 ditions so diverse both biologically and physically. But, curiously enough, as Darwin has 

 remarked^ coral reefs are, for some reason, not favourable to them. Yet a number of species 

 may be taken there, and some are even characteristic and specially modified for the habitat. 

 Among these may be included the LitJiotryas which bore into coral rock, those species of 

 Pyrgoma which live imbedded in reef corals, and several of the a^^twm-group of Balanus, 

 besides common species such as B. tintinnahulam and B. amphitrite. Of course those which 

 live on animals such as sea-snakes or turtles and on floating objects as cuttle-bones or 

 pieces of wood, are also found. 



The collection contains 16 species, including members of all the groups mentioned above. 

 Of these species two are new. Most of the others have already been recorded from some 

 part of the Indo-Pacific region, but one form can only be classed as a variety of the West 

 Indian Lithotrya dorsaUs, and another, whose locality has hitherto been unknown, was 

 formerly supposed to be (and still may be) West Indian. 



Family Lepadidae. 

 Genus Lepas Linn., 1758. 



1. Lepas ansifera Linn., 1767. Darwin, i. p. 81'. 



Taken on floating objects in various localities throughout the Archipelagoes, a number 

 of the younger individuals being on cuttle-bones. 



Genus Dichelaspis Darw., 1851. 



2. Dichelaspis warwicki (Gray), 1825. Darwin, i. p. 120. 



The specimens differ from that figured by Darwin in that the upper end of the 

 occludent segment of the scutum is considerably wider than the base of this segment, leaving 

 only a narrow strip of soft skin between itself and the basal segment. But Darwin says 

 that this segment may be wider in the upper part. The jjlate at the base of the carina 

 is an independent ossicle, joined by a sutui-e to the true keel. 



Taken in Suvadiva Atoll. 



3. 1 Dichelaspis grayi Darw., 1851. Darwin, i. p. 123. 



A specimen which I believe to belong either to this species or to D. peUucida Darw., 

 1851, is attached to a sea-snake {Hydrus platurus) taken by the expedition in the Maldives. 



Unfortunately, the shells are so badly preserved, owing to their having been kept in 

 formalin, that it is impossible to be certain of the species. It is the habit of both species 

 to live on sea-snakes. 



1 All the references to Darwin's work in this paper are to his " Monograph of the Cirripedia," London, 1851-4. 



