394 MOLLUSCA SUB-KINGDOM VI 
This family, so well known under the preoccupied name Cyprinidae, 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 : Plewro- 
phorinae and Veniellinae. 
Pleurophorus, King (Fig. 700). Elongated, sub-rectangular ; beaks sub-terminal ; 
surface smooth or with radial sculpture ; hinge with two cardinal teeth in each valve; 

Pleurophorus costatus, King. Permian ; Fic. 701 
Byers Quarry, England. 4A, Shell, 1/; ae 
(after King). B, Internal cast from Gera, Anisocardia elegans, Mun.-Chalm. Kimmeridgian ; 
Thuringia (after Geinitz). Cap de la Heve, near Havre. 1/3. 
anterior adductor scars deep, with a buttress-like ridge behind it. Devonian to 
Trias ; especially abundant in the Permian. 
Cypricardella, Hall (Microdon, Hall); Mecynodon, Keferst.; Cypricardinia, Hall. 
Devonian. Astartella, Hall. Carboniferous. 
Anisocardia, Mun.-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 



US Fic. 702. 
: > . . . . . 
YS _—S—s— Arctica islandica, Lin. Pleis- 
tocene; Bohuslain, Sweden. 


hy) Fic. 703. 
Venilicardia cordiformis, Fic. 704 
Orb. Gault;  Seignelay, ‘ if , 
Yonne. Veniella tumida, Nyst. Crag; Antwerp 
valve with a forwardly directed anterior and a posterior cardinal tooth. Jura to 
Tertiary. 
Roudairia, Mun.-Chalm. Like Trapeziwm, but with a sharp keel and smooth area 
behind, anteriorly with concentric ridges; right posterior cardinal bifid. Upper 
Cretaceous. 
