390 



MANUAL OF ZOOLOGY. 



The inner surface of the valves of the shell is lined by ex- 

 pansions of the integument which secrete the shell, and are 

 called the " lobes " of the " pallium," or " mantle." The diges- 



to a stone {alter uaviason; : p reauncie ; v ventral vaive ; a -uorsai vaive 

 Crania Ignabergensis, attached by its ventral valve to a piece of coral (Chalk), 



tive organs and muscles occupy a small space near the beak 

 of the shell, which is partitioned off by a membranous septum, 

 which is perforated by the aperture of the mouth. The re- 

 mainder of the cavity of the shell is almost filled by two long 

 oral processes, which are termed the "arms," and from which 

 the name of the class has been derived (fig. 204, D). These 

 organs are lateral tubular prolongations of the margins of the 

 mouth, usually of great length, closely coiled up, and fringed on 

 one side with ciliated lateral processes, or "cirri." In many 

 Brachiopods the arms are supported upon a more or less com- 

 plicated internal calcareous framework or skeleton, which is 

 sometimes called the " carriage-spring apparatus," and which 

 in many extinct forms is coiled into a shelly spiral. 



The mouth conducts by an oesophagus into a distinct 

 stomach, surrounded by 'a well-developed granular liver. The 

 intestine has a "neural flexure," and "either ends blindly in 



