THE ARCHIPELAGO OF CHAUSEY. 39 



they are removed from their native element. The 

 Turbo, the Buccinum, with its brown and white 

 markings, the Rissoa, with its small, closely- twisted 

 shell, and the Acorn shell*, with its pyramidal test, 

 covered every stone and rock. In sheltered nooks I 

 found the pretty little rose-coloured Cowrie, and 

 large Chitons f, animals in which the back is covered 

 by a solid cuirass composed of moveable pieces like 

 the olden greaves. Then there was the ThetysJ, a 

 kind of sea slug of a fine orange colour, which bears 

 its tuft of branchiae on the hindermost part of the 

 back, and the Haliotis, with its nacreous shell, sur- 

 rounded by a triple row of fringes. The vaulted 

 roof of the little caverns, which had been formed by 

 the crumbling away of the rocks, was clothed with a 

 mammillated stratum of Simple Ascidians, a species of 

 molluscs which live and die without ever having 

 moved from the same spot ; while from this bright red 

 ceiling there hung, like so many girandoles, trans- 

 parent crystal-like Clavellinas, and the bright Botrylli, 



* The acorn shells (Balanus) constitute a genus of the class of 

 the Cirripedes animals allied in many respects to the Crustacea, 

 but which undergo certain metamorphoses, which led Cuvier, even 

 after he had studied their anatomy, to place them amongst the 

 Mollusca. The discovery of their true nature is due to the Irish 

 naturalist, J. W. Thomson (see his Zoological Researches and 

 Illustrations). 



f The Cowries (Cyprcea), which are well known to all conchologists 

 and amateur shell collectors, are molluscs belonging to the class of 

 the Gasteropods. Chitons belong to the same class of molluscs, and 

 are remarkable for the division of their test, or shell, which exhibits 

 a series of imbricated semicircular rings placed along the back. 



J The Thetys belongs to the same class, but it has no trace of a 

 test. 



D 4 



