8 



PYRGOMA. 

 GENERIC CHARACTER: Shell sessile, of ons piece sub- 

 globular, bulging, convex above, tbe top perforated with 

 a small orifice, which inclines to oval. Cover with four 

 valves, scarcely apparent. 



* P. ANGLICUM. Magazine of Natural History, O S., vol. 



I, p. 475. It is rare that a full grown and complete 

 Caryopbyllia Smithii (a species of coral) is brought from 

 moderately deep water, without having a few specimens 

 seated on its diverging plates; audi have rarely seen it 

 under other circumstances. 



PEDUNCULATED CIRRHIPEDA. 



The shell supported by a tubular stalk, the base attached 

 to some foreign body. 



ANATIFERA. 

 GENERIC CHARACTER: The shell compressed at the 



sides, with 5 plates, which are contiguous and unequal ; 



the lower side plates largest. This genus is also termed 



Anatifa, and Auatifer. 



* A. LEVIS. Lepas Anatifera. Turt. Lin. Pen. Brit. Zo., 



vol. 4, pi. 38. fig. 9. Stew. Elem., vol. 2, p. 364. Mont. 



Test. Brit., vol. 1, p. 15. A. L. Crouch's In., pi. 1, 



fig. 18. Barnacle. 



This which is termed the Duck or clustering Barnacle, 

 is the largest of the British species, sometimes measuring 

 from the base of the shell to the point 2| inches; and to 

 distinguish it from the next, with which it is commonly 

 confounded, it should be remarked as being more robust, 

 and larger, while the stalk is comparatively shorter. The 

 union of the larger plates is equal, and their margin rises 

 forward in a rounded shape, again descending with a sweep; 

 while in the next species the hinge is formed by the over- 

 lapping of one of the plates; and their margin without rising 

 passes forward, obliquely descending to the opening. In 

 the latter also, the anterior plate leaves a larger membranous 

 space at its produced portion, where it passes between the 

 dorsal plate and the larger lateral. The dorsal plate of A. 

 Levis is more ridged and elevated: the edge amounting to 

 a keel at its bend. The graining on the surface of the 

 plates, the absence of which in the present species has been 

 deemed of sufficient importance to afford a trivial name, 

 cannot be depended on for distinction. This species is found, 

 sometimes in immense numbers, attached to wood that has 

 been floating on the ocean; but instances of their occurrence 

 are not nearly so frequent, as of the next species. Each 

 kind is found occupying its own separate wreck, and may 

 readily be distinguished, the present species by the clustering 

 of its young on the stalk or shell of the parent, while on 



