448 



MOLLUSCA 



PHYLÜM VI 



Sub^^enera: Adinopteria, Leiopteria, VertiLmnia Hall. Devonian. Pteronites WQoy. 

 Devonian and Carboniferous. ? Rittotia de Kon. Carboniferous. Oxytoma Meek (Fig. 6/8). 

 Trias to Cretaceous. Mcleagrina Lam. Jura to Recent. 



Limoptera Hall (Monopteria Meek ; Myalinodonta, Parops 

 wing reduced, posterior large. Devonian and Carboniferous. 



ffililert). Anterior 



Fig. 677. 

 Pteria contorta 

 (Porti.). Rhae- 

 tic; Kössen, 

 Tyrol. 



Fici. 678. 



Pteria (Oxytoma) costata Sow. Great Oolite 

 Luc, Calvados. 



Fig. 679. 



Pseudomonotis ecliinata Sow. Cornbrash 

 (Oolite) ; Button, England. 



Pteroperna Morris and Lycett. Middle Jura. 



Pseudomonotis Beyr. {Eumicrotis Meek) (Fig. 679). Left valve fiat, anterior wing 

 not developed or minute. Devonian to Cretaceous, 



Gassianella Beyr. (Fig. 680). Left valve inflated with prominent incurved beak ; 



Fig. 680. 



Gassianella gryphaeata (Münst.). Upper Trias 

 St, Cassian, Tyrol. 



Fig. 681. 

 Monotis salinaria (Schloth.). Red 



Alpenkalk (Norian) ; 

 Bavaria. -j^. 



Berchtesgaden, 



the right Hat or concave, witliout byssal sinus ; teeth small as in Pteria, but more 

 numerous ; area ampliidetic, wide. Trias. 



Monotis Bronn (Fig. 681). Equivalve, compressed, radially striate, witli low, sub- 

 central beaks ; anterior wing indistinct, rounded ; posterior wing short, truncate or 

 oblique. Trias. 



Halohia Bronn {Daonella Mojs.) (Fig. 682). Equivalve like Monotis, but the 



Halohia {Daonella) lommeli Wissm. Lower Keuper (Norian) ; 

 Wen gen, South Tyrol. 



Fig. 683. 



Posidonomya hecheri Bronn. Culm Measures : 

 Herborn, Nassau, i/^. 



anterior wing only represented by a smooth non-projecting area (Halohia), or botli 

 wings absent (Daonella). Abundant in the Trias. 



