BKACH10PODA. 



225 



Prof. King first pointed out the existence of calcarions spires in several Tere- 

 bratulce of the older rocks, and others have been discovered by MM. Quen- 

 stedt, De Koninck, and Barrande. In form they resemble Terebratulina, 

 Eudesia, and Lyra. 



Fig 136. Retzia serpentina, D. K. Fig, 137, Uncites gryphus. 



UNCITES, Defrance. 



Type, U. gryphus, PL XV. fig. 17. Fig 137. Fossil, Devonian. Europe. 

 Shell impunctate ; oval, bi-convex, with a long incurved beak ; foramen 

 apical, closed at an early age; deltidium, large, concave; spiral processes 

 directed outwards ; no hinge- area. 



The large, concave deltidium of Uncites so much resembles the channel 

 formed by the dental plates of Pentamerus, that Dalman mistook the shell 

 for a member of that genus. The discovery of internal spires, by Prof. Bey- 

 rich, shows that it only differs from Retzia in being impunctate and destitute 

 of hinge-area. Some of the specimens have corresponding depressions in the 

 sides of the valves (fig. 137, p) forming pouches which do not communicate 

 with the interior. 



FAMILY III. RHYNCHONELLID.E. 



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 deltidium, sometimes concealed; hinge.teeth supported 



Fig. 138. R. nigricans. Fig. 139. Ventral: Dorsal. 



Fig. 138. Dorsal valve with the animal; a, adductor muscles : i, intestine. 



Fig. 139. R. psittacea, interiors, s, septum ; /, foramen ; d, deltidium; t, teeth; 

 t, sockets'; c, oral lamellse; a, adductor impressions ; r, cardinal; p, pedicle muscles ; 

 o, ovarian spaces. 



