BRACSIOPODA* 



375 



Dalman mistook the shell for a member of that genus. The 

 discovery of internal spires, by Professor Beyrich, shows that it 

 only differs from Retzia in being impunctate and destitute of 

 hinge-area. Some of the specimens have corresponding depres- 

 sions in the sides of the valves (Pig. 173, ^), formiD.g pouches 

 which do not communicate with the interior. 



PaMILY III. — EHYN"CHOKELLrDJE. 



8heU impunctate, oblong, or trigonal, beaked ; ' hinge-line 

 curved ; no area ; valves articulated, convex, often sharply 

 plaited; foramen beneath the beak, usually completed by a 



Pig. 174. R. nigricans. 



Ventral. 



Fig. 175. 



Dorsal. 



Fig. 174. Dorsal valve with the animal ; a, adductor muscles ; i, intestine. 



Fig. 175. R. psittacea, interiors. 5, septum ; /, foramen ; d, deltidium ; t, teeth; V, 

 sockets ; c, oral lamellae ; a, adductor impressions i r, cardinal ; p, pedicle muscles ; 0, 

 ovarian spaces. 



deltidium, sometimes concealed; hinge-teeth supported by 

 dental plates ; hinge-plate deeply divided, supporting oral 

 lamellae, rarely provided with spiral processes ; muscular im- 

 pressions grouped as in Terebratula ; vascular impressions 

 consisting of two principal trunks in each valve, narrow, 

 dichotomising, angular, the principal posterior branches inclos- 

 ing ovarian s aces. 



Animal [of Rhynchonella) with elongated spiral arms, directed 

 inwards, towards the concavity of the dorsal valve ; alimentary 

 canal terminating behind the insertion of the adductor in the 

 ventral valve ; mantle not adhering, its margin fringed wit i a 

 few short setae. 



EHYiq-cHOKELLA, Pischer. 



Synonyms, Hypothyris, Phil. Hemithyris (psittac3aj, 

 D'Orbigny. Acanthothyris (spinosa), D'Orbigny. Cyclothyrii 

 (latissima), M'Coy. Trigonella (part), Pischer (not L. nor Dx 

 Costa). 



