162 MANUAL OF NATURAL HISTORY. 



V. CLASS.— BRACHIOPODS (Brachiopoda). 



Animal furnished with a pair of ciliated oral 

 arms, sometimes supported by a calcareous append- 

 age ; respiration performed by the vascular mantle ; 

 body covered with two shells. Attached to marine 

 objects. 



S UB-CLASS. — Ancylopod-Brachiopods (Ancylopoda). 

 Oral arms recurved and attached to fixed appen- 

 dages on the disc of ventral valve ; shell with nu- 

 merous minute perforations. 



I. ORDER. — Ancylobrachiate-Brachiopods 



(Ancylobrachiata). 



Oral arms affixed to calcareous plates, forming 



hoops attached to the hinge-margin of the ventral 



valve, and prominent in its cavity. 



1. Family. — Lamp-Shells (Terebratulidae). Arms 



looped or contorted, fixed to an apophysary 



skeleton; shell regular, valves articulated, 



attached by a tendinous band which passes 



out of a hole in upper valve. 



II. ORDER — Cryptobrachiate-Brachiopods 



(Cryptobrachiata). 



Oral arms sunk into grooves in the convex centre 

 of the inner surface of the ventral valve. 

 1. Family. — Thecidians (Thecidseidae). Arms con- 

 torted, fixed to margin of apophysary ribs 

 and cardinal teeth ; shell attached by apex 

 of lower valve, which is produced. 



