CLASS I 



PELECYPODA 



447 



Tliis family diflers from the Pteriidae cliiefly by its multivincular ligament in the adult 

 state. It linds its maximum development in the Jura and Cretaceous. 



Bakewellia King. Small, obliquely elongated, alate behind, three to four den- 

 ticulations under the beaks. Permian. 



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

 terminal, pointed, with obscure dental ridges sub-jiarallel 

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



Subgenus Roernesia Laube (Fig. 673). With a strong tooth 

 under the beak and subtaxodont denticulations on the pos- 

 terior cardinal liorder. Trias. 



Odontoperna Freeh. Quadrate with two to three 

 oblique dental folds below the beaks. Trias. 



Pedal-ion Solander (Jsognoinon Klein ; Perna Brug. ; 

 MuUetia Fisch.) (Fig. 674). Equivalve, subquadrate, . . ,. ,^ ,,, „ ^ 



. , . , ° . . ,1 ,1 J . 1 Hoernesia sociahs (Schlotli.). 



With terminal beaks, an anterior byssal notch, edentulous Muscheikalk ; wtirzburg, Bavaria, 

 hinge, and numerous ligamentary grooves. Trias to Recent. 



Edentula Waag. Alpine Trias. Pernostrea Munier-Chalmas. Jura. 



Inoceramus Sowerby {Catillus 

 Brong. ; Haploscapha Conr. ; Neo- 

 catillus Fisch.) (Fig. 675). Rounded 



Pig. 673. 



Fig. 674 



Pedalion soldanii (Desh.). Oligocene ; Waldbockellieim, 

 near Krenznach, Prussia, i/.i. 



Inoceramus cripsi 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 : Adinoccramus Meek (Fig. 676), with radial sculp- 

 ture ; Volviceramus Stol. ; Anoimea Eichw. ; Haenleinia Biihm. 



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



Pliocene and Recent. 



Family 21. Pteriidae Meek. 



Shell avicnloid, bialate, monomyarian, mequivalve, with an 

 alivincular ligament ; the byssus issuing by a notch in the smaller 

 valve ; the young dimyarian, the anterior adductor disappearing 

 with age. Silurian to Recent. 



Pteria Scopoli {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. 



Fig. 676. 



Actinoceraimis sulcatus 

 Park. Gault ; Perte dii 

 Rhone, Ain. l/j. 



