CLASS BRACHIOPODA. 



55 



bases of the spiral " arms," and which is sometimes called 

 the " carriage-spring-apparatus." The larger valve lies 



Fig. 22. — Terebratula {Waldheimia) flavescens. A, The shell viewed from 

 behind, showing the smaller valve, and the perforated summit of the 

 larger valve above it. B, Inner view of the smaller valve, showing the 

 shelly loop (?) which supports the spiral arms. C, Inner view of the 

 larger valve, showing the foramen or aperture (/) in the beak, through 

 which the muscular stalk of attachment passes. D, Longitudinal and 

 vertical section of the animal, showing the spiral arms (a), the stomach 

 (s), and the liver {h). At /is the opening in the beak, with the stalk of 

 attachment (p) passing through it. After Davidson and Owen. Some 

 details have been omitted in figs. B, C, and D, for the sake of cieamess. 



upon the lower surface of the animal, and has its beak 

 perforated by a large rounded aperture (fig. 22, C, /). 

 Through this opening passes a muscular stalk, by which 

 the shell is firmly fixed to some foreign body (fig. 22, D, 



The animal contained within this shell exhibits many 

 peculiarities of structure, but none is more striking than 



