1 86 COLLEGE ZOOLOGY 



Because of their shell they were for a long time regarded 

 as mollusks. The valves of the shell, however, are dorsal 

 (Fig. 126, d.v.) and ventral (v.v.) instead of lateral as in the 

 bivalve mollusks (Fig. 173). Within the shell (Fig. 127) is 

 a conspicuous structure called the lophophore (2), which consists 

 of two coiled ridges, called arms; these bear ciliated tentacles 



FIG. 127. Anatomy of a BRACHIOPOD, Waldheimia australis. i, mouth; 

 2, lophophore; 3, stomach; 4, liver tubes; 5, median ridge on shell; 6, heart; 

 7, intestine; 8, muscle from dorsal valve of shell to stalk; Q, opening of nephrid- 

 ium; 10, stalk; n, body-wall; 12, tentacles; 13, coil of lip; 14, terminal 

 tentacles. (From Shipley and MacBride.) 



(12). Food is drawn into the mouth (i) by the lophophore. A 

 true ccelom is present, within which lie the stomach (j), digestive 

 gland (4), and the heart (6). 



The group BRACHIOPODA is extremely old, and, although found 

 in all seas to-day, brachiopods were formerly more numerous in 

 species and of much greater variety in form than at present. 

 Some of them, for example Lingula, are apparently the same 

 to-day as they were in the Silurian period estimated at about 

 twenty-five million years ago. 



10. GEPHYREA 



The GEPHYREA (Gr. gephura, a mound) are worm-like animals 

 that have been classed by many zoologists with the Phylum 

 ANNELIDA (Chap, XI). Their relations to this phylum are, 



