LESSON 45.] NUTRITION IN THE BRACHIOPODA. 159 



assumed by the central arm (e). To the right of the figure fe seen a 

 large orifice the tubular portion of the left arm, which has been 

 removed. The anterior and posterior portions of the mantle are 

 external in each direction (/). The trumpet-shaped mouth (a) is 

 seen just below the tendinous portion of one of the four strong mus- 

 cles (6), whose function it is to close the valves, and, crossing it ob- 

 liquely, a muscle of the second pair ; the white, glistening character 

 of the tendons of these muscles is very beautiful. The mouth leads 

 to a pharynx, and a very short oesophagus, which instantly terminates 

 in the stomach. The biliary follicles (c), as before seen, completely 



FIG. 256. 



FIG. 25T. 



Alimentary canal, Terebratula Aus- 

 tralis, front view. 



Terebratula Australia, side view. 



conceal the stomach, and the short, trumpet-shaped intestine (h) may 

 be traced to its termination within the mantle. The peduncle for 

 attachment (g) is seen as before. 



701. A better view of the alimentary canal is given in Pig. 257, 

 from a preparation of these organs dissected out of the body. Here 

 the mouth is seen surrounded with short, unusually strong cilia (a) ; 

 living and breathing under the weight and pressure of from sixty to 

 ninety fathoms of water, the cilia of the arms require to be strong 

 to compel the necessary currents of water to perform the circuit of 

 the interior of the valves ; charged with oxygen, for the supply of 

 the respiratory organs, it is, at the same time, laden with food (ani- 



