340 ACEPIIALA PALLIOBRANCIIIATA, 



tubular cirrhated arms. They do not, however, effect 

 any change of place by these organs, which cannot be 

 said to be feet, but are extended processes springing from 

 the margins of the mouth, and therefore analogous to the 

 labial palps of other bivalves. These curious organs are 

 in some Brachiopods quite free ; in others, attached to 

 a complicated cartilaginous or calcareous skeleton. None 

 of the existing mollusks of this order are capable of 

 changing place. Exclusive of their brachial apparatus, 

 their bodies are but small. The digestive organs and 

 nervous system are simple ; there is no foot ; the sexes 

 are distinct ; the organs of sex are attached to the 

 mantle. The lobes of the mantle line, and usually ad- 

 here to the valves of the shell, which are not to be re- 

 garded as exactly homologous with those of other bivalves, 

 but each as the equivalent of two half valves of a Lamel- 

 libranchiate Mollusk. The surface of the mantle is covered 

 with vibratile cilia?. The muscular system is variously 

 developed in different genera. Ocelli and otolitic vesicles 

 are certainly present in some species, if not in all. The 

 history of their developement is unknown. Their food 

 is infusorial. 



The most striking feature of the animals of this great 

 section — their possession of spiral fringed arms — was first 

 noticed by Pallas in a Terehratula, and by Otho Frederic 

 Miiller in a Crania. The researches of Cuvier into the 

 external structure and anatomy of Lingula recalled at- 

 tention to the group, and that famous naturalist clearly 

 perceived its importance. Not, however, until the great 

 comparative anatomist of England, Professor Owen, aided 

 by the invaluable collections of Hugh Cuming, who will 

 ever rank among the foremost of benefactors to Mala- 

 cological science, undertook a minute inquiry into the 



