PHYLUM BRACHIOPODA 



Classes 



1. Inarticulata 



2. Articulata 





Orders 



Atremata. 

 Neotremata. 

 Protremata. 

 Telotremata. 



In the Brachiopods the soft parts of the animal are en- 

 closed in a shell which is formed of two parts termed valves, 

 one placed on the dorsal surface, the other on the ventral. 

 Generally the main part of the body occupies only the pos- 

 terior portion of the shell. The interior of the shell is 

 lined by a membrane, the mantle, which is a prolongation 

 of the body-wall, and is divided into two lobes, one oc- 

 curring in each valve ; the space between the two is 

 known as the mantle-cavity. In most genera the margin 

 of the mantle is thickened, and carries numerous chitinous 

 setae. The mouth (fig. 69, v) opens into the mantle-cavity, 

 and leads into an oesophagus, which is followed by a 

 stomach (partly surrounded by the liver), and an intestine. 

 In the articulate brachiopods the intestine is short and 

 ends blindly, in the inarticulate forms it is long and ends 

 in an anus which opens into the mantle-cavity. The nervous 

 system consists of a ring round the oesophagus, with gang- 

 lionic enlargements from which nerves are given off to the 

 arms, mantle, etc. The part of the body-cavity which 



