394 



MOLLUSCA 



SUB-KINGDOM VI 



This family, so well known under the preoccupied name Cyprinidac, probably shared the 

 same origin as the Astartidae, and the two do not definitely separate until the Jura. The 

 position of the Palaeozoic ancestors is necessarily doubtful, and they are placed differently 

 by different authors. The group may be conveniently divided into two sub-families : Pleuro- 

 phorinae and Veniellinac. 



Pleurophorus, King (Fig. 700). Elongated, sub-rectangular ; beaks sub-terminal ; 

 surface smooth or with radial sculpture ; hinge with two cardinal teeth in each valve ; 



FIG. 700. 



Pleurophorus costatus, King. Permian ; 

 Byers Quarry, England. A, Shell, l/l 

 (after King). B, Internal cast from Gera, 

 Tlmringia (after Geinitz). 



FIG. 701. 



Anisocardia elegans, Mun. -Chalm. Kimmeridgian 

 Cap de la Heve, near Havre, i/i 



Devonian to 



anterior adductor scars deep, with a buttress-like ridge behind it. 

 Trias ; especially abundant in the Permian. 



Cypricardella,' Hall (Microdon, Hall) ; Mecynodon, Keferst. ; Cypricardinia, Hall. 

 Devonian. Astartella, Hall. Carboniferous. 



Anisocardia, MuiL-Chalm. (Fig. 701). Rounded or trapezoid, plump, smooth or 



radially striate ; posterior slope some- 

 times keeled ; hinge with a strong some- 

 times bifid right cardinal behind, and an 

 anteriorly directed front cardinal; left 



FIG. 702. 



Arcticn islandicn, Lin. Pleis- 

 tocene ; Bohuslan, Sweden. 



FIG. 703. 



Venilicardia conliformis, 

 d'Orb. Gault ; Seignelay, 

 Yonne. 



FIG. 704. 

 Vcniello. tumida, Nyst. Crag ; Antwerp 



valve with a forwardly directed anterior and a posterior cardinal tooth. Jura to 

 Tertiary. 



Roudairia, Mun.-Chalm. Like Trapezium, but with a sharp keel and smooth area 

 behind, anteriorly with concentric ridges ; right posterior cardinal bifid. Upper 

 Cretaceous. 



