CLASS I 



Geromya Ag. (Fig. 738). 



A-. .Middle Juni, Zii 

 jaczki, Poland. i/i- 



PELECYPODA 



Cordalc, iiillal 



Fki. 737. 



Crrss/i/,,, htfirnsin, 

 Ai^-. Lowcr Oülite 

 Tainiie, öartlie. i/i- 



465 



], witli i'atlici' aiilcrior, |iI(i.-(il;\ rous 

 --; hiii^v iiiai\^iii u\ ilic ri^lit valve 

 ri(»r, (■(Iciiluious, Ijiil willi a blunt 



Fir;. 738. 



Ceromija cf. aalcnsls Queiist. Middle Jura ; 



Kneuttingeu, Lonaine. Hinge, 1/2' 



elongated process in front of an internal callosity. Chiefly occnrring as moulds. Jura. 



Family 2. Pholadellidae Miller (eniend.). 



Shells obovate, usually attenuated hehind and slightly gaping, hinge margin thin, 

 edentulous, ligament parivincular, external ; posterior adductor scar large. Paleozoic. 



Allorisma King. E longa te, arcuate, tlie pallial line sinuated, anterior side 

 sliorter, sometimes witli a liinule ; sciüpture strengest mesially. Carboniferous and 

 Permian. 



Ehytimya Ulricli, Elongate, sub-quadrate, concentrically waved, tbe waves 

 stronger anteriorly ; sculptnred on the posterior half witli 

 radiating series of grannies ; lunnle very narrow. Silurian. 

 Pholadella and Gimitaria Hall. Devonian ; North 

 America. 



Family 3. Pholadomyacidae Gray. 

 Shell suhstance nacreous and cellulo - crystalline ; gills 



Pliolniloiin/ii. vnnrh:.«!,,; S( 

 MiddltNJui-a; l'iezclinow, l-olai 

 Vi. 



completely united, hehind, forming a septurii heloiv the anal chamher ; foot small, with an 



opisthopodium ; siphons long, united to their tips, not wholly retradile, naked ; ventral 



commissure of the mantle ivith a pedal and an opisthopodial foramen. Shell thin, equi- 



VOL. I ' 2 H 



