CLASS I 



PELECYPODA 



447 



This family differs from the Pteriidae chiefly by its multivinciilar ligament in tlie adult 

 State. It linds its niaximum development in the Jura and Cretaceous. 



Bahewellia King. Small, obliqiiely eloii-^Mlud, alate Ijehind, tliree to four den- 

 ticulations iinder the beaks. Pernnan. 



Gervülia Defr. (Fig. 672). Posterior wing obscure, hinge plate thick, beaks 

 terminal, pointed, with obscure dental ridges siib-parallel 

 to the long axis of the valve. Trias to Eocene, 



Subgenus Hoernesia Laube (Fig. 673). With a streng tooth 

 under the beak and subtaxodont denticulations on the pos- 

 terior Cardinal border. Trias. 



Fig. G73. 



Odontoperna Frech. Quadrate with two to three 

 oblique dental folds below the beaks. Trias. 



Pedalion Solander (Jsognomon Klein ; Perna Brug. ; 

 Mulletia Fisch.) (Fig. 674). Equi valve, subquadrate, 

 with terminal beaks, an anterior byssal notch, edentulous Muschelkalk ^"würzburg, Bavaria. 

 hinge, and numerous ligamentary grooves. Trias to Recent. 



Alpine Trias. Pernostrea Munier- Chalmas. Jura. 



Inoceramus Sowerby (Gatillus 

 Brong. ; Haploscapha Conr. ; Neo- 

 catülus Fisch.) (Fig. 675). Rounded 



Fio. 674. 



Pedalion soldanii (Desh.). Oligocene ; Waldböckelheim, 

 near Kreuznach, Prussia. 1/2. 



hwceramus cHpsi Mant. Upper Cretaceous 

 Gosau, Austria. 1/2 natural size. 



with concentric sculpture ; prominent, rather anterior beaks, 

 and edentulous hinge bearing numerous small ligamentary pits. 

 Jura, and especially the upper and middle Cretaceous. 



Subgenera ; Actinoceramus Meek (Fig. 676), with radial sculp- 

 ture.; Volviceramus Stol. ; Anopaea Eichw. ; Haenleinia Böhm. 



Grenatula Lam. Thin-shelled, elongate, smooth. Jura (?), 



Pliocene and Recent. 



Family 21. Pteriidae Meek. 



Shell aviculoid, Malaie, monomyarian, inequivalve, with an 

 alivincular ligament ; the hjssus issuing hy a notch in the smaller 

 valve ; the yonng dimyarian, the anterior adductor disappearing 

 with age. Silurian to Recent. 



Pteria Scopol! (Avicula Brug.) (Fig. 677). Cardinal 

 border in the young with pseudocardinal and lateral teeth, becoming more or less 

 obscure with growth ; shell thin, oblique. Devonian to Recent. 



A et inoceramus sulcatus 

 Park. Gault; Perte du 

 Rhone, Ain. i/j. 



