282 NOVEMBER 



sites, which acquire a great size in the course of a voyage 

 of only a few months. 



The valves resemble delicate shells, and are elegantly 

 painted with various tints of light blue varied with white, 

 the edges of the valves being often rich scarlet or orange. 

 The hand is deep purplish black, the fingers stout and 

 massive ; but not differing in their structure or in their 

 mode of use, from those of their sessile fellows. 



Perhaps the most interesting of all our native forms 

 of these Cirripedes for true parasitism is always a sub- 

 ject of peculiar interest is that little species 1 which 

 invariably selects as its support the stony walls of a 

 coraL Our beautiful Cup-coral, so common at extreme 

 low-water level on both the north and south coasts of 

 Devon and Cornwall, is the favourite species of the 

 Pyrgoma. So far as my experience goes, extending over 

 a very extensive series of specimens, I think about one 

 in six of these corals carries the parasite, generally situ- 

 ated either on, or just without, the margin of the cup! 

 I say, "generally," because Mr. Guyon has lately re- 

 corded what he thinks an exception to the rule, in two 

 Pyrgomata situated on the rock close to the base of the 

 coraL But Mr. Holdsworth, an excellent authority, con- 

 siders that the exception is more apparent than real 



1 Pyrgoma Anglicum, of which three specimens are seen attached to a 

 Caryophyllia Smithii, at the left side of Plate xxxi. 



