WALDHEIMIA. 



169 



process. Through a hole in this process there projects a peduncle 

 which fastens the animal to a foreign body, such as a rock. A side 

 view of the two shells recalls the appearance of a Roman lamp, with 

 the peduncle as a wick ; hence the Brachiopoda are sometimes termed 



^ig- 97- — Ventral (A) and Dorsal (B) Shell of Waldheimia 

 Australis. (After Davidson.) 



Lamp-shells. The two shells are hinged upon each other at the posterior 

 end (towards the peduncle) and can be widely opened anteriorly. The 

 shells and the animal are piano-symmetric, about a perpendicular plane 

 passing through the middle line of each shell. (The bivalve Mollnsca 

 are piano-symmetric, about a plane passing betiveen the shells, which 

 are therefore right and left^ not dorsal and ventral. ) 



Inside the dried dorsal shell can be seen a complex calcareous 

 skeleton in the form of a twisted loop. The growth of the shell is like 

 that of bivalves. The cavity inside the shells is lined by a soft double 

 flap of the body called the mantle, enclosing the mantle-cavity. Its 

 edge is fringed with seta. 



The most conspicuous part of the body is the lophophore, which 

 consists of a pair of coiled arms carrying a great number of ciliated 

 tentacles. A ridge lying dorsal to the mouth, the epistoine, is continued 

 round the lophophoral arms. The mouth leads into a short oesophagus, 

 a swollen stomach, and a short intestine which ends blindly. There is 

 a pair of large racemose digestive glands, with ducts leading into the 

 stomach. The ccelom is spacious, and the same parts of the mesoderm 



