396 MOLLUSCA SUB-KINGDOM vi 



4 



Opis, Defr. (Fig. 709). Trigonal, cordate, smooth, or concentrically striate ; beaks 



Astarte (Goodallia) 

 miliaris, Defr. Eocene ; 

 Grignon, near Paris 

 (after Desbayes). ] 



FIG. 706. 



Astarte (Crassinellct) obliqua, Desh. 

 Inferior Oolite ; Bayeux, Calvados. 



Woodia profunda, Desh. 

 Eocene ; Aizy, near Laon. 

 A, Hinge, enlarged. B, 

 Shell. 



prominent, prosocoelous ; lunule very deep, bordered by a keel ; FIG. 709. 



cardinal teeth long, narrow (2 : 1). Trias to Cretaceous. Opis Goidfussiana, 



/-v n -i T n T 7 Tk-r d'Orb. Upper % Jura ; 



Opisoma, fetol. Jura, keebachia, ISeumayr. Cretaceous. Nattheim. 



Family 5. Crassatellitidae. Dall. 



Shell as in the Astartidae, but the valves always somewhat unequal, and usually 

 more or less rostrate, the beaks compressed, erect, or opisthocoelous ; ligament internal, 



FIG. 710. 

 Crassatellites plumbea, Chem. sp. Eocene (Calcaire Grossier) ; Damery, near Epernay. 2/3. 



more or less obsolete, resilium large, wholly internal, attached at each end to a chondro- 

 phoric pit in the hinge plate behind the cardinal teeth ; lateral teeth and sockets usually 

 alternated in the valves, the hinge plate heavy, flat ; the posterior cardinal in the right 

 valve very small or obsolete, with no distinct socket in the opposite valve ; full cardinal 



formula R1 Q 101 - Lower Cretaceous to Recent. 



The earlier forms of this family have a small resilium close to the nearly marginal liga- 

 ment. With time, later ones show a gradual descent of these organs, until in some of the 



