304 MANUAL OF NATURAL HISTORY. 



duncle elongated, naked, fleshy, contractile ; 

 body compressed, the sides protected by shelly 

 plates (2.1. 2). (Anatiferidce, Gray.) 

 2. FAMILY. Ramphidian- Barnacles (Ramphidi- 

 onidae). Peduncle short, hard, wrinkled or 

 scaly ; body compressed, protected by trian- 

 gular shelly plates. (Pollicipidce, Gray.) 



II. ORDER BURROWING- CIRRHOPODS (Terebrantia). 



Body naked, attached to the upper wall of a cham- 

 ber, excavated by the animal in some foreign sub- 

 stance, and communicating with the water by an 

 orifice. 



1. FAMILY. Burrowing - Barnacles (Alcippidse). 

 Cirrhi six, composed of three articulations, 

 the last simple ; branchiae setaceous, attached 

 to the external surface of the upper lip. 



III. ORDER. SESSILE-CIRRHOPODS (Sessilia). 



Body not peduncled, enclosed in a cylindrical or 

 cone-shaped tube formed of one or more shelly 

 valves ; aperture closed by a two- or four-valved 

 operculum. 



1. FAMILY. Coral-Barnacles (Pyrgoinatidse). Shell 



composed of a single undivided cone ; aper- 

 ture small ; operculum of two or four pieces ; 

 base calcareous, cup-like or tubular. Para- 

 sitic on madrepores. 



2. FAMILY. Acorn-Shells (Balanidse). Shell com- 



posed of six or eight valves, more or less 



