WALDHEIMI4. 169 
process. Through a hole in this process there projects a peduncle 
which fastens the animal to a foreign body, such asa rock. A side 
view of the two shells recalls the appearance of a Roman lamp, with 
the peduncle as a wick ; hence the Brachzopoda are sometimes termed 
Fig. 97.—VENTRAL (A) AND Dorsar (B) SHELL or Waldheimia 
Australis, (After DAVIDsON. ) 
a, Adductor. a, Adductor. 
a', Apex. 2, Loop. 
6, Ventral Adjustor. Pp, Septum. 
c, Divaricator. 7 s, Socket. 
J, Foramen. 
o, Peduncular Muscles. 
t, Teeth. 
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 plano-symmetric, about a perpendicular plane 
passing through the middle line of each shell. (The bivalve Mollusca 
are plano-symmetric, about a plane passing Je¢ween the shells, which 
are therefore zzght and eft, 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 mule, enclosing the manéle-cavity. Its 
edge is fringed with sete. 
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 epzstome, is continued 
round the lophophoral arms. The mouth leads into a short cesophagus, 
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 
