Order II. MOLLUSCA. ACEPHALA. 
Section I. BRACHIOPODA. 
Shell With two valves ; lobes of the cloak free anteriorly ; arms is- 
suing from between the lobes at the margin of the month ; all the 
species are marine and permanently attached. 
Pedunculata. 
a. Shell supported on a fleshj peduncle. 
Lingula. 
h. Peduncle passing through the apex of one valve. 
Terebratula. 
Spirifer. 
Magas. 
Sesselia. 
Discina. 
Criopus. 
Obscure genera, apparently free, and extinct. 
Pentamerus. 
Productus. 
