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, Frech. Quadrate with two to three 
oblique dental folds below the beaks. Trias. 
Perna, Brug. (Isognomon, Klein; Mulletia, Fisch.), 
Hoernesia socialis, Schloth. sp. Fic. 625) E ee 5 eae ith torenanel 
Muschelkalk ; ‘Wiraburg, Bavaria. (Fig. 625). quivalve, sub-quadrate, with termina 
beaks, an anterior byssal notch, edentulous hinge, and 
numerous ligamentary grooves. Trias to Recent. 

Fia. 624. 

Fig. 626. 
Inoceramus Cripsi, Mant. Upper Cretace- 
ous ; Gosau, Austria. 1/, natural size. 

Fic. 625. 
Perna Soldanii, Desh. Oligocene; Waldbéckelheim, near 
Kreuznach, Prussia. 1/9. 
Pernostrea, Munier-Chalmas. Jura. 
Inoceramus, Sow. (Catillus, Brong.; Haploscapha, Conv. ; 
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. 

Sub-genera: Actinoceramus, Meek (Fig. 627), with radial sculp- 
ture ; Volviceramus, Stol. ; Anopaea, Kichw. 
Fic. 627. 
Crenatula, Lam. Thin-shelled, elongate, smooth. Jura (?), _ eed Brig 
1, ne ‘ark. 7ault 5 erte du 
Pliocene, and Recent. Rhone. 1). 
Family 21. Pteriidae. Meek.! 
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. 
XVIIT-), 1895: 
