874 



MAlftrAL OF THE MOLLUSCA. 



Suh-genus? Merista, Suess. Ter. scalprum, Eoemer. (A. 

 cassiclea, Quenst. Sp. plebeia, Ph.) Silurian 

 — Devonian. Europe. Shell impunctate, 

 dental plates {v) and dorsal septum {d) suj)- 

 ported by arched plates ("shoe-lifter" 

 processes, of King) which readily detach, 

 leaving cavities (as in Fig. 171) ; spiral arms 



Fig. 171. Merista. have been observed in all the si)ecies. 



Eetzia, King. 



Dedicated to the distinguished Swedish naturalist, Eetzius. 



Type, Ter. Adrieni, Vern. 



Example, E. serpentina, Carb. L., Belgium, Fig. 172. 



Shell punctate, terebratula-shaped ; beak truncated by a 

 round foramen, rendered complete by a distinct deltidium; 

 hinge-area small, triangular, sharply defined; interior with 

 diverging shelly spires. 



Fossil, about 50 species. Silurian — Trias. South America, 

 United States, Europe. 



Professor King first j)ointed out the existence of calcareous 

 spii'es in several Terehratulce of the older rocks, and others have 

 been discovered by MM. Quenstedt, De Koninck, and Barrande. 

 In form they resemble Terchratulina, Eudesia, and Lyra. 



Fig. 1 72. Bctzia serpentina, D. K. 



Fig. 173. Vncitcs gri/j hits. 



Uncites, Defrance. 



Type, U. gryphus, PI. XV., Fig. 17. Fig. 173. 



Eossil, Devonian. Europe. 



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

 beak ; foramen apical, closed at an early age ; deltidium laige, 

 concave ; spii-al processes directed outwards ; no hinge-area. 



The large, concave deltidium of Uncites so much resembles 

 the channel formed by the dental plates of Pmtamcrus, that 



