BRACHIOPODA. 207 



Class BRACHIOPODA.* 



Animal furnished with a pair of cirrated arms or oral append- 

 ages, whicli are free or united by membrane, sometimes supported 

 by calcareous processes. Mantle-lobes closely applied to the valves, 

 fringed with horny sctcc, and supplied with branching veins, gills 

 none, respiration performed by the vessels of the mantle. Foot 

 none. 



Shell inequivalve, attached to submarine bodies by a muscular 

 peduncle, or by the suljstance of its ventral valve ; valves dorsal and 

 ventral, united by muscles, and usually articulated by teeth. Ma- 

 rine. 



The class takes its name from the long fringed organs which are 

 attached near the mouth, and are regarded as designed to bring 

 food to the mouth. Tlie valves are generally considered as upper 

 and lower, instead of right and left, as in other bivalves, the larger 

 one, which often has a long curved beak out of which the pedicle 

 issues, being the lower one. By others, however, they are consid- 

 ered as anterior and posterior. There are but few species living at 

 the present day, but they are found in a fossil state in great abun- 

 dance throughout the rocks of many geological periods. 



Family TEREBRATULID^. 



Shell round or oval, lower valve with a prominent beak and two 

 curved hinge teeth ; upper valve with a hinge process, and a shelly 

 loop to which the arms are attached. 



Genus TEREBRATULINA, D'Orb. 1847. 

 Shell punctured, oval, with a faint central depression and radiat- 

 ing ribs ; Ijcak large with a large aperture bounded in part by the 

 end of the upper valve ; hinge of one oblique tooth in the upper 



* All relating to the Brachiopods was prepared for the press by Dr. Gould. — W. G. B 



