CHAPTER V 



THE CIRRIPEDIA 



SUB-CLASS CIRRIPEDIA, Burmeister (1834). 



Order 1. Thoracica. 



Sub-Order 1. Pedunculata. 

 2. Operculata. 



Tribe 1. Asymmetrica. 



2. Symmetrica. 

 2. Acrothoracica. 

 3. Ascothoracica. 

 4. Apoda. 

 5. Rhizocephala. 



Definition. Crustacea which are sessile in the adult condition; the 

 carapace (very rarely absent) forms a mantle completely enclosing 

 the body and limbs, usually strengthened by shelly plates ; the 

 posterior limbless part of the trunk is vestigial and usually ends in 

 a caudal furca ; the antennules are organs of attachment, becoming 

 vestigial in the adult, and the antennae generally disappear ; man- 

 dibles without palp ; typically six pairs of biramous cirriform trunk- 

 limbs ; usually hermaphrodite, female genital apertures on first 

 trunk-somite, male apertures behind last pair of limbs ; paired eyes 

 absent in adult ; development with metamorphosis ; young generally 

 hatched in nauplius stage and passing through a so-called " cypris 

 stage " with bivalved shell. 



Historical. Some of the Cirripedia are sufficiently common and 

 conspicuous to have attracted attention from remote times. They 

 are probably referred to by Aristotle, and they formed the subject 

 of a curiously persistent mediaeval myth, current in literature from 

 the twelfth to the beginning of the eighteenth century, regarding 

 the origin of the Barnacle Goose. While the earlier systematists 

 not unnaturally classed the barnacles and acorn-shells as Mollusca, 

 it seems strange to find this view of their affinities surviving the 



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