CLASS I 



PELECYPODA 



499 



Mya Liun. (Fig. 827). Smooth externally. Tertiary and Recent. 



Subgenera 



Platyodon Com-ad. Surface decussated, siphon with horny appendages. 

 Cryptomya Conrad. Small, the ]iallial line discrepant in the two valves. Siihenia Turton. 

 Minute, byssiferous, nestling. Tugonia Gray. Tertiary and Recent. 



Family 42. Corbulidae Fleming. 



Shell small, mxich as in Mya, hit the pallial line feeble or obsolete, the ligament 

 usually sub-external, separated from the resilium, xvhich is internal, alivincular and 

 amphidetic ; the chondrophore 

 is received into a socket of the 

 opposite valve, not merged with 

 the valve margin ; hinge ivith 

 one or two sub-umbonal pro- 

 jecting teeth, and rarely obscure 

 traces of laterals ; the posterior 

 gape inconspicuous ; siphons 

 short, united, naked, tvholly 

 retractile. Trias to Recent. 



Corhula (Bicorhula) gallica Lam. 

 Calcaire Glossier; Damery, near 

 Epernay, France. Hinge, i/i. 



A, 



Fio. 829. 

 Corhula carinata Duj. 



Miocene ; Potzleinsdorf, near 

 Vienna. B, C. angiv^tata Sow. 

 Upper Cretaceous ; Gosau. 



Corbula Lam. (Figs. 828, 

 829). Small, ovate, rostrate, very inequivalve, tlie right valve convex, larger, with a 

 prominent tooth in front of the pit for the resilium, left valve with a flattened 

 chondrophore, and usually a posterior tooth. Trias to Recent. 



Subgenera: Erodona Daudin {Azara d'Orb. ; Potamnniya Sow.). Pallial sinus obsolete, 

 fluviatile. Pleistocene and Recent. Bothrocorhula Gabb. With a lunule deeply indented 



into the cavity of the valves. Tertiary and Recent. 



Fl<:. .S30. 



Pannpc menardi Desli. Miocene; Vienna Basin. A, Dorsil view 

 of valves. B, Internal mould. C, Hinge-plate seen from above, 1/2. 



Corhulamclla Meek. "With an anterior 

 myophore. Cretaceous. Aniso- 

 thyris Conr. {Fachydon Gabb). 

 Pliocene. Paramya Conr. ; Cor- 

 hiclomya Nyst. Tertiary and 

 Recent. 



Family 43. Saxicavidae 



Gray. 



Shell substance as in Mya ; 

 epidermis conspicuo^is ; valves 

 equal, free, rude and often 

 irregular, more or less elon- 

 gated and gaping, not fully 

 covering the animal ; adductor 

 .^cars often irregular, the pallial 

 line discontinuous or irregular, 

 the sinus distinct; shell raar- 

 gins smooth ; area obsolete ; 

 ligament and resilium external, 

 parivincular, seated on strong 

 nymfhs, sometimes tcidely ex- 

 tended ; hinge without laterals, 

 ivith few feeble or obsolete sub- 

 umbonal cardinals. Creta- 

 ceous to Recent. 



Saxicava Fleuriau {Glycimeris Schum. ; Hiatella Daudin ; Byssomya Cuvier ; 

 Agina Tiirton). Hinge edentulous in the adult, with one or two cardinals in the 



