CLASS I 



PELECYPODA 



469 



lunule before the beaks ; valves closed, pallial sinus shallow, obscure ; sii^hons short, 

 separate ; marine. Tertiary to Recent. 



Pecchiolia Meuegli. Shell heavy ; beaks spirogyrate, distant ; sculpture radial. 

 Eocene ; Alabama. Miocene ; Europe. 

 Euciroa Dall. Recent, abyssal. 



The genera Verticordia Wood ; Tri(jonulvna d'Orl). ; Haliris Uall ; and (?) Allo- 

 pagus Stol. {Hippagus Desh., non Lea) are included under the family Verticordiidae. 

 Tertiary and Recent. 



Equivalve, oval, thin, in- 



Family 13. Poromyacidae Dall. 



Shell rounded, nacreous and cellulo -crystalline, granular or smooth externally ; hinge 

 with obscure tubercles in front of the resilimn ; ligament external, opistliodetic ; resilium 

 sub-internal beloiv the ligament, with a small lithodesma ; area obscure or absent ; a 

 depressed false lunule in front of the beaks; valves nearly or entirely closed; pallial 

 sinus small or obsolete; marine. Cretaceous to Recent. 



Liopistha Meek {Oymella, Psilomya Meek) (Fig. 747). 

 flated, concentrically or 

 radially striated, gaping 

 and compressed behind ; 

 beaks prominent, in- 

 curved ; hinge with a 

 nymph and projecting 

 process on each side ; 

 ligament sunken, partly 

 external. Cretaceous. 



(?) Basterotia Mayer 

 {Eucharis Recluz, non 



Peron). Valves sub-equal, closed, with a strong tooth in the right and two in the 

 left ; surface granular ; form trapezoid. Miocene and Recent. 



Poromya Forbes {Embla Loven). Ovate, plump, surface granular ; pallial line 

 irregularly widened, not sinuate. Eocene and Recent. 



Dermatomya Dall. Surface smooth, with a conspicuous periostracum ; pallial 

 line sinuate. Recent, abyssal. 



Cetomya, Getoconcha Dall {Silenia Smith). Recent, aby.ssal. 



Fit.. 747. 

 Lio^nstha freqiiens Zitt. Upper Cretaceous ; Gosau, Austria. Vi- 



Family 14. Ouspidariidae Dall. 



Shell sub-equivalve, rostrate, earthy or cellulo-crystalline, rarely with surface granula- 

 tions; hinge edentulous or 'with sub-umbonal tubercula- 

 tion, sometimes bicttressed ; ligament sub-internal, anterior 

 to the beaks or obsolete; resilium internal, with a mesial 

 or ventral lithodesma ; area amphidetic or obscure ; valves 

 closed except at the tip of the rostrum ; pallial line simple ; 

 siphons united ; marine. Jura to Recent. 



Guspidaria Nardo (Neaera Gray ; Ryderia Wilton) 

 (Fig. 748). Shell concentrically sculptured ; hinge 

 with a small posteriorly inclined chondrophore in each 



valve, and an elongated ridge behind it ; ligament always anterior to the beaks 



when present. Jura to Recent. 



Subgenera : Cardiomya Adams ; with radial sculpture and a posterior lateral tooth in 

 the right valve. Leiomyn Adams ; smooth, with an anterior cardinal in each valve, and 



Fir;. 748. 



Cuspulnria cuspidata Olivi 

 Miocene ; Baden, near Vienna. 



Vi- 



