CLASS TUNICATA. 



255 



CLASS IV. BRACHIOPODA.* 



Fig. 1*37. 



General Characteristics. The Brachiopods (arm- 

 footed) have the valves on the upper and the 

 under side of the body, instead of the later- 

 al ; are without a hinge ligament, the valves 

 opening and shutting by a complicated ar- 

 rangement of muscles ; respire by blood- 

 vessels ramifying minutely over the surface 

 of the mantle ; and obtain their food, in 

 most species, by two long spiral arms, capable 

 Fig ASS ^ being unrolled and extended 

 to a great distance. 



The Terebratulidae (boring 

 family) have the back of the ven- 

 tral valve pierced with a hole for the passage of 

 the pedicle, by which the animal is permanently 

 attached to solid substances. 



The Lingulidae (tongue-shape) have a long 

 pedicle issuing from the interior of the shell 

 through the hinge. 



Fig. 



Dorsal valve of a 



Brachiopod, with 



one spiral arm 



partly uncoiled. 



Terebratulina 



feptentiiondlis, 



Lamp-shell. 



Lingula anafina. 



CLASS V. TUNICATA. 



General Characteristics. The Tunicata (cloaked) 

 have no shell, head, feet, or arms, and usually look like 

 shapeless gelatinous masses, composed of two tunics or coat- 

 ings, forming a tube, with one orifice for the inlet and 



* Prof. E. S. Morse, endorsed by some other Naturalists, classes the Brachiopode 

 with the Annelids. 



