444 



MOLLUSCA 



PHYLUM VI 



or frequently obsolete in the adult, though j^rescnt in the young; generally Ossiferous ; 

 hinge schizodont or edentulous. The young sometimes showing a distinct neinonic stage. 

 Marine. 



Family 15. Pterineidae Dall. 



Shell fteriiform, bialate, dimijarian, the anterior adductor smaller ; inequivalve, very 

 inequilateral; dentition obscure; ligament amfliidetic, external, multivincular (?) ; the 

 hyssus passing through a notch in the smaller valve. Ordovician to Devonian. 



In Plerinea and its allies Ave have the first indications of divergence of what ultimately 

 became taxodont and schizodont dentition. • From this assemblage, as indicated by Jackson, 

 a large ijrojjortion of the Prionodesmacea have diverged in various directions. It is probable 

 that from tliis source the filibranchiate Taxodonts have sprung, rather than directly from the 

 foliobranchs. 



Rhombopteria Jackson (Fig. 666). Posterior wing sej)arated from the body of the 



A B 



Fifi. 666. 



Rliomliopteria mira 

 (BaiT.). Silurian (B); 

 Prague, Bohemia (after 

 Jackson). 



Fig. 667. 



A, Pterinca laci'is Goldf. Devonian ; Niederlahnstein, Nassau. Interior of left 

 valve, i/i- B, P- lineata Goldf. Same locality ; external view. 



valve by a shallow sinus ; anterior wing short ; teeth obscure, the posterior elongated. 

 Silurian. 



Pterinea Goldf. (Fig. 667). Left valve convex, right valve flat ; hinge plate long, 

 broad, auriculate before and behind ; area amphidetic, grooved ; ligament j)arivin- 

 cular (?) ; anterior teeth obscure, transverse ; the posterior elongate, nearly parallel to 

 the cardinal margin, depressed behind. Posterior adductor scar large, the anterior 

 small but strong, inserted below the anterior wing. Ordovician to (carboniferous ; 

 particularly abundant in the Devonian of Europe and America. 



Actinodesma Saitdb. (Glyptoclesma, Ectenodesma Hall ; Dolichoptcron Maurer). 

 Like Pterinea, Ijut with tlie wings elongated and pointed. Devonian. 



Leptodesma, Hall ; Kochia Freeh (Onychia, Sandb.; Loxopiteria Fi'ecli). Devonian. 



Family 16. Lunulicardiidae Fischer. 



Usually equivalve, triangular shells %oith terminal beetles, from which a sharp ridge 

 runs toward the lower margin, bounding a, flattened area. Hinge margin straight, long. 

 Internal characters unhioivn. Silurian and Devonian. 



Lunulicardium Miinst. Anterior side with a byssal sinus. Silurian and 

 Devonian. L. semistriatum Miinst. 



Patrocardium Fischer (Hemicardium Barr., non Cuvier). Without byssal sinus. 

 Silurian. 



Additional genei-a : Amita (Spanila, Tetinhi), Mila, TenJca, Babinlca (Matercula) 

 Barrande. Silurian. 



