190 SYSTEMATIC ZOOLOGY. 



ORDER II. BRACHIOPODA (Lamp-shells). 



From the fact that the Brachiopoda possess a bivalve 

 shell, these forms were formerly included among the 

 molluscs near the clams. A little examination, however, 

 shows that the resemblance between them is but slight. 

 The two valves of the Brachiopod are unequal in size, and 

 are dorsal and ventral, rather than right and left, as in the 

 clams. Near the point where the two parts (valves) are 

 hinged together there is usually an opening * in the larger 

 valve through which a fleshy peduncle or stalk projects, 



by means of which the animal is 

 fastened to some support. In- 

 side the valves, which can be 

 closed by muscles, are the prin- 

 cipal organs. Near the mouth 

 are found a number of delicate 

 ^ tentacles (much like those of the 



33. A New rLingland 



Brachiopod (Terebratulina P l V Zoa) , the disc which bears 

 septentmonalis). J 



them being frequently rolled into 



a spiral. The alimentary canal is bent, but a vent is 

 occasionally lacking. 



The Brachiopods are all marine. There are few in 

 existing seas; but they are among the oldest inhabitants 

 of the earth, for the shells are found fossil in great num- 

 bers in all rocks from the earliest down to the present 

 time. 



SUMMARY OF IMPORTANT FACTS. 



1. The group of VERMES is not a natural one, but an 

 association for convenience. Its members are bilaterally 

 symmetrical and have distinct dorsal and ventral sur- 



* In some the peduncle extends from between the valves instead 

 of having a special opening. 



