ORDER I PRIONODESMACEA 379 
Schizodus, King (Fig. 651). Ovate or quadrate, smooth ; lateral teeth not fluted ; 
anterior adductor scar with a small radial buttress. Abundant in the Permian. 
Myophoria, Bronn (Neoschizodus, Gieb.), (Figs. 652, 653). 
Smooth or radially sculptured, usually with a strong 
radial ridge extending from the umbones backward and 
downward to the basal margin ; the sculpture on the areas 
thus separated usually dis- 
crepant. Beaks mesogyrate, 



Fic. 651. 
Myophoria laevigata, Myophoria decussata, Miinst. 
Schizodus obscurus, Sow. Zechstein; Nieder- Alb. sp. Schaumnkalk ; Upper Trias; St. Cassian, Tyrol. 
rodenbach, near Hanau. 4A, Cast, 1/j. B, Ridersdorf, near A, Exterior of right valve, 1/;. 
Hinge, 1/; (after King). Berlin. 1/;. B, Enlarged view of hinge. 
lateral teeth fluted, muscular scars buttressed by feeble ridges. Abundant in the Trias. 
Sub-genus : Myophoriopsis, Wohrmann. 
A) 
\\ \\) ‘ 
AY NN 
AN ( 
Fic. 654. Fic. 655. 
Trigonia navis, Lam. Lower Brown Jura; Gun- Trigonia daedala, Park. Middle Cretaceous 
dershofen, Alsace. 1/}. (Hervien); Meule de Bracquegnies, Belgium. 1/}. 
Trigonia, Brug. (Figs. 654-658). Surface sculptured with nodulose ribs or rows of 

Fic. 656. 
Fic. 658 
Trigonia costata, Sow. Fic. 657. Trigonia pectinata, 
Middle Jura; Wurtemberg. Trigonia, ef. aliformis, Park. Senonian ; Lam. Recent; <Aus- 
1/y. Vaels, near Aix-la-Chapelle, 1/). tralia. Hinge, 1/;. 
pustules, the posterior dorsal area usually discrepant with the rest. Beaks opistho- 
