370 



MOLLUSCA 



SUB-KINGDOM VI 



Gervillia, Defr. (Fig. 623). Posterior wing obscure, hinge plate thick, beaks 

 terminal, pointed, with obscure dental ridges sub-parallel 

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



Sub-genus Hoernesia, Laube (Fig. 624). With a strong 

 tooth under the beak and sub-taxodont denticulations on the 

 posterior cardinal border. 



Odontoperna, Freeh. Quadrate with two to three 

 oblique dental folds below the beaks. Trias. 



Perna, Brug. (Isognomon, Klein; Mulletia, Fisch) 

 Hoernesia socialis, Schloth. sp. /,-,. on ,\ P . 

 Muschelkalk ; Wiirzburg, Bavaria. (* l g- 625). .Lquiyarve, sub - quadrate, with terminal 



beaks, an anterior byssal notch, edentulous hinge, and 

 numerous ligamentary grooves. Trias to Recent. 



FIG. 624. 



Inoceramus Cripsi, Mant. Upper Cretace- 

 ous ; Gosau, Austria. 1/2 natural size. 



FIG. 625. 



Perna Soldanii, Desh. Oligocene ; Waldbockelheim, near 

 Kreuznach, Prussia. i/ 2 . 



Pernostrea, Munier-Chalmas. Jura. 



Inoceramus, Sow. (Catillus, Brong. ; Haploscapha, Conr. ; 

 Neocatillus, Fisch.), (Fig. 626). Rounded with concentric sculp- 

 ture ; prominent, rather anterior beaks, and edentulous hinge 

 bearing numerous small ligamentary pits. Jura, and especially 

 the upper and middle Cretaceous. 



FIG. 627. 



Actinoceramus sulcafiis, 

 Park. Gault ; Perte du 

 Rhone, 1/1- 



Sub-genera : Actinoceramus, Meek (Fig. 627), with radial sculp- 

 ture ; Tolviceramus, Stol. ; Anopaea, Eichw. 



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

 Pliocene, and Recent. 



Family 21. Pteriidae. Meek. 1 



Shell Aviculoid, bialate, monomyarian, inequivalve, 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. 628). Cardinal border in the young with 

 pseudocardinal and lateral teeth, becoming more or less obscure with growth ; shell 

 thin, oblique. Devonian to Recent. 



1 Bittner, A., Lamellibranchiaten der Alpinen Trias (Abhandl. k. geol. Reichsanstalt, Bd. 

 XVIIL), 1895. 



