BEACHIOPODA, 



375 



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

 discovery of internal sjDires, 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 (Fig. 173, p), forming pouches 

 which do not communicate with the interior. 



, Family III. — Rhynchonellid^. 



{^hdl impunctate, oblong, or trigonal, beaked ; hinge-lino 

 cuiTed ; no area ; valves articulated, convex, often sharj)ly 

 phaited; foramen beneath the beak, usually completed by a 



Fig. 17-1. II. nigricans. 



Ventral. 



Fig. 175. 



Dorsal. 



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



Fig. 175. K. psittacea, interiors, s, septum ; /, foramen ; d, deltidium ; t, teeth; V, 



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



ovarian spaces. 



deltidium, sometimes concealed; hinge-teeth su2">ported by 

 dental plates; hinge-plate deeply divided, sui^porting oral 

 lamellae, rarely provided with spiral processes ; muscular im- 

 pressions grouped as in Terebratula ; vascuLar imi^ressions 

 consisting of two principal trunks in each valve, narrow, 

 dichotomising, angular, the principal posterior branches inclos- 

 ing ovarian spaces. 



Animal {otPilnjnclionella) 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 wifi a 

 few short setDO. 



Rhynchokella, Fischer. 



Synonyms, Hj^oothyris, Phil. Ilemithyi'is (psittac^aj, 

 D'Orbigny. Acanthothyris (spinosa), D'Orbigny. Cycloth^-rii 

 (latissima), M'Coy. Trigonella (part), Fischer (not L. nor Dj 

 Costa). 



