BRACHIOPOD As 375 
Dalman mistook the shell for a member of that genus. The 
discovery of internal spires, by Professor Beyrich, shows thatit 
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. 
FamIty III.—RHYNCHONELLIDZ. 
Shell impunctate, oblong, or trigonal, beaked; hinge-line 
curved; no area; valves articulated, convex, often sharply 
plaited; foramen beneath the beak, usually completed by a 
Fig. 174. &. nigricans. Ventral, Fig. 175. Dorsal. 
Fig, 174. Dorsal valve with the animal; a, adductor muscles ; 7, intestine. 
Fig. 175. R. psittacea, interiors. s, septum ; 7, foramen ; d, deltidium ; ¢, teeth; ¢’, 
sockets; c, oral lamelle; a, adductor impressions ; 7, cardinal; p, pedicle muscles; 9a, 
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 yalve, narrow, 
dichotomising, angular, the principal posterior branches inclos- 
ing ovarian spaces. 
Animal (of Rhynchonella) with elongated spiral arms, directed 
inwards, towards the concayity of the dorsal valve; alimentary 
canal terminating behind the insertion of the adductor in the — 
ventral valve; mantle not adhering, its margin fringed with a 
few short sete. 
RHYNCHONELLA, Fischer. 
Synonyms, Hypothyris, Phil. Hemithyris (psittacea), 
D’Orbigny. Acanthothyris (spinosa), D’Orbigny. Cyclothyris 
oi M‘Coy. Trigonella (part), Fischer (not L. nor Da 
osta). 
