484 RECENT BRACHIOPODA chap. 



of his laboratory. The Lingula place themselves vertically; the 

 anterior end of the body just reaches the level of the sand ; 

 the three lobes into which the orifice of the tube is divided cor- 

 responding with the three brushes of setae which project from 

 the anterior rim of the mantles. These setae are described by 

 Morse as projecting in the form of three funnels ; currents of 

 water are seen continually passing in at the side orifices and out 

 through the central. The tube consists of two portions : an 

 upper part, which is flattened to correspond with the flat shape 

 of the body, and a lower part, in which the stalk lies. The 

 upper part is lined with a layer of mucus, but the sand is not 

 glued together to form a definite tube. The lower part of the stalk, 

 or the whole when the animal is contracted, is lodged in a 

 definite tube composed of grains of sand agglutinated by mucus, 

 probably secreted from the walls of the stalk. At the least sign 

 of danger the stalk is contracted violently, and the body is 

 withdrawn to the bottom of the upper portion of the tube. The 

 rapid retreat of the animal is followed by the collapse of the 

 sand at the mouth of the tube, and all trace of the presence of 

 the Lingula is lost. 



The shells of this species are frequently rotated through a 

 small angle upon one another, a movement which is prevented 

 in the Testicardines by the hinge. In very young transparent 

 specimens Francois was able to observe the movements of the 

 fluid in the system of tubules which penetrate the mantle ; these 

 tubules are figured by him, and Fig. 315 is taken from his 

 illustration. 



Davidson in his Monograph on the British Fossil Brachi- 

 opoda states that the largest "recent Brachiopod which has 

 come under my notice is a specimen of Waldheimia venosa 

 Solander, measuring 3 inches 2 lines in length, by 2 inches in 

 breadth, and 1 inch 11 lines in depth." It was found in the 

 outer harbour of Fort William, Falkland Islands, in 1843. A 

 specimen of Terebratula grandis from the Tertiary deposits, how- 

 ever, exceeds this in all its dimensions. Its length was 4J 

 inches, its breadth 3 inches 2 lines, and its depth 2 inches 2 

 lines. 



Distribution in Space 



Brachiopods are very localised ; they live in but few places, 



