CATALOGUE 
OF 
BMCHIOPODA OE LAMP-SHELLS 
IN 
THE BRITISH MUSEUM. 
Class 11. BRACHIOPODA. 
Shell inequivalve, equilateral, attached by a muscular peduncle, 
or by the surface of one valve, or free ; valves applied to the 
dorsal and ventral sides of the animal, imited by muscles and 
mostly articulated by teeth ; dorsal valve* usually smallest, always 
free, furnished internally wdth sockets for the hinge-teeth, and 
with shelly processes t for the support of the animal ; ventral 
valve usually largest, and with its umbo produced and perforated 
for the passage of the peduncle, frequently attached by its outer 
surface, and generally provided internally with two prominent 
teeth j periostracum thick, sometimes developed into concentric 
lamellae. 
Animal furnished with elongated labial appendages, or oral 
arms, which are free or united by membrane and variously folded, 
* 'Vt'hat is here called the dorsal valve has often been called the lower 
valve, being usually below when the animal is in its natural position 
attached to marine bodies ; but it has been found to cover the back of 
the animal. 
t Sometimes termed an “ internal skeleton ” or “ apophysary 
system.” 
B 
