THE CLASSIFICATION OF ANIMALS 53 



phylum Bracttiopoda. These are represented by few species 

 at the present time ; all are inhabitants of the sea, and nearly 

 all of them live at the bottom of comparatively deep water. 

 They are of no economic importance whatever. But in past 

 time, as evidenced by their fossil remains, they must have 

 swarmed in the seas, and in certain places on the coast of the 

 West of Ireland every stone which is lifted from the beach 

 contains a fossil Brachiopod. They are therefore familiar to 

 all collectors of fossils, and since their bodies were protected by 

 two shelly valves they present a considerable resemblance to 

 bivalve Mollusca ; and it is somewhat of a shock to learn that 



FiG. 23. A, shell of Brachiopod viewed from above to com- 

 pare with J5, the shell of Pelecypod or bivalve Mollusc 

 viewed from the side ; d, upper and anterior valve of 

 Brachiopod shell ; v, lower and posterior valve. 



the scientific zoologist regards them as members of a distinct 

 phylum with no relation to the Mollusca whatever. An ex 

 animation of tne living forms shows that the two valves of the 

 Brachiopoda are upper or dorsal and lower or ventral, not right 

 and left as in Mollusca j that there is no foot, but that a stalk 

 arises from the posterior part of the body by which the animal 

 is permanently anchored to the rock on which it lives. Further, 

 the secondary body-cavity is exceedingly wide and spacious, 

 whilst the primary body-cavity or blood-system is very small 

 and difficult to detect. In fact the internal organisation of a 

 Brachiopod has more resemblance to that of an Annelid than 

 to that of a Mollusc ; and in this connection it may be men- 

 tioned that in the edges of the mantle-folds of Brachiopods 



