BRACHIOPODA 



265 



in position. The animal is attached to some more or less fixed object bj' 

 means of the peduncle, a stout, muscular stalk which is a prolongation of 

 the hinder end of the body and passes either between the valves of the 

 shell or through a hole in the projecting ventral valve; in a few species 

 (Crania) the whole ventral valve is attached, no peduncle being present. 

 The soft parts of the body, which lie between the hinder and middle 

 portions of these shells, are very short and broad, and from them two 

 leaf-like folds called the dorsal and the ventral mantles extend forwards 

 and cover the inner surface of the forward portion of the shells. Two 

 additional projections of the anterior body wall also extend forwards and 

 occupy the space between the two mantles. These are the tentacular arms 

 or lophophores, a pair of ridges or of bent or coiled arms which in the 



.0, 



Fig. 437 — Diagram of a brachiopod (Delage et Herouard). 1, peduncle; 2, dorsal 



shell ; 3, stomach ; 4, liver ducts ; 5, mouth ; 6, mantle ; 7, gills ; 



8, lophophore ; 9, muscles ; 10, intestine ; 11, ventral shell. 



Testicardines are supported by a calcareous skeleton proceeding from the 

 dorsal valve of the shell. These arms are the largest and most conspicuous 

 organs in the body and have given the group its name : they are respiratory 

 and sensory in function, and are also of use in the ingestion of food. 

 Both they and the mantles contain a cavity which is in direct communi- 

 cation with the body cavity. Running along the surface of each ridge or 

 arm is a ciliated groove along one side of which is a row of ciliated ten- 

 tacles. By the action of these cilia the minute organisms which form the 

 food of the animal are swept into the mouth. 



The mouth lies between the base, of the arms and is without special 

 jaws or lips; it opens into a digestive tube in which an oesophagus, stom- 

 ach, and intestine may be distinguished. Sac-like digestive glands (livers) 

 open into the stomach. The Testicardines have no anus : in the Ecardines 



