444 



MOLLUSCA 



PHYLUM VI 



or frequently obsolete in the adult, thoiujh iiresent in the young ; generally hyssiferous ; 

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

 Marine. 



Family 15. Pterineidae Dali. 



Shell pteriiform, Malaie, dirayarian, the anterior adductor smaller ; inequivalve, very 

 inequilateral ; dentition ohscure ; ligament amphidetic, external, multivincular (?) ; the 

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



In Pterinea and its allies we have the first indications of divergence of what ultimately 

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

 a large proportion 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. 



Rhomhopteria Jackson (Fig. 666). Posterior wiiig separated from tlie body of the 



A B 



Fio. 666. 



Rh(ynibopteria mira 

 (Barr.). Silurian (E) ; 

 Prague, Bohemia(after 

 Jackson). 



Fio. 667. 



A, Pterinea laevis Goldf. Devonian ; Niederlahnstein, Nassau. Interior of left 



valve, Vi- -B, P- Uneata 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, riglit valve flat ; hinge plate long, 

 broad, auriculate before and behind ; area amphidetic, grooved ; ligament parivin- 

 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. 



Äctinodesma Sandb. {Glijptodesma, Ectenodesma Hall; Dolichopteron Maurer). 

 Like Pterinea, but with the wings elongated and pointed. Devonian. 



Leptodesma Hall ; Kochia Frech {Onychia Sandb.; Loxopteria Frech). Devonian. 



Family 16. Lunulicardiidae Fischer. 



Usually equivalve, triangulär shells with terminal healcs, from which a sharp ridge 

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

 Internal characters unknown. Silurian and Devonian. 



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

 Devonian. L. semistriatum Münst. 



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

 Silurian. 



Additional genera : Amita {Spanila, TetinJca), Mila, Tenha, Bahinha {Matercula) 

 Barrande. Silurian. 



