170 



SESSILIA. 



contiguous and unequal ; the lower lateral ones the largest; 

 the whole of theui united and kept together by means of 

 thin membranes. 



Anatifa Icevis. — The Smooth AnatiFxV. Plate XIX. 

 fig, 5. With tive smooth valves ; the dorsal valve rounded 

 at the sides, and slightly earinated; peduncle very long, of 

 a scarlet colour. Inhabits the British seas. 



This and other species, popularly called Barnacles, were formerly 

 supposed to give origin to ducks and geese, the filaments having been 

 taken for feathers. 



ORDER n.-SESSEIA. 



Body without a peduncle, and enclosed in a multivalv-e 

 shell, seated immediately on marine bodies, or rocks ; mouth 

 and tentacula placed in the apex, or upper part of the body. 



* With a bivalve operculum. 

 Genus l.—FYRGOMA.—Savl</ny. 



Generic Character. — Sessile, univalve, subglobular, ven- 

 tricose, convex above, and open at the apex ; opening small, 

 elliptical, provided with a bivalve operculum. 



Pyrgoma crenata — The Crenated Pyrgoma. Plate 

 XIX. fig. 6. With radiated ribs, and crenated round the 

 margins ; of a pale violet colour. 



Geyius 2.— CREUSIA Leach. 



Generic Character. — Body sessile, su'bglobular, enclosed 

 in an operculated shell; having three or four pairs of ten- 

 tacular arms. Shell sessile, fixed, orbicular, convexo-coni- 

 cal, consisting of four united unequal valves; operculum 

 internal and bivalve. 



Creusia verruca The Warted Creusia. Plate XIX. 



fig, 7. White, slightly depressed, with interlocked obliquely 



