THE BRACHIOPODS 78 



an opening near the back of the lower shell, vr betAveen the shells. 



In some forms this stalk is very small and serves merely to 

 attach the creatures to rocks, etc., while in others it is used in bur- 

 rowing through sandy beaches. The intestine curves around and 

 opens, if at all, on the right side near the mouth. There is a well 

 developed liver and one or two pairs of tubular kidneys, while the 

 heart lies above the stomach. 



The Parchment Shell, (Tcrebralnlina septentrional is, Fig. 43 J, 

 is a Brachiopod, and is extremely abundant off the Xew England 

 coast, on rocky bottoms at depths between 100 and 500 feet, and it 

 is also found off the northern coasts of Europe. At first sight it 

 resembles a little bivalve with elongate, slightly heart-shaped 

 shells, of yellowish color, resembling old parchment The shells 

 are marked with faint radiating ridges, and the lower shell projects 

 backward beyond the apex of the upper. The Brachiopod is 

 attached to rocks, etc., by means of a stalk-like body which i:)rojects 

 backward through an opening near the narrow apex of the lower 

 shell. In life the shells move quite freely over each other and often 

 gape open, displaying the beautiful feathered "arms" or gills which 

 lie coiled within the cavity of the shells. This little creature is not 

 more than an inch long and three-quarters of an inch wide. The 

 eggs are laid in the water, and develop into minute free-swimming 

 larvae covered with moving cilia, and having a tuft of bristles at 

 the head end. The Ijod}^ is pear-shaped, with two constrictions. 

 Soon the creature cements itself to the bottom by the posterior end 

 of the body, and two folds which are to secrete the shells, one on 

 the back and the other on the lower side, grow upward and en- 

 close the bod v. 



