CLASS I 



PELECYPODA 



469 



lumde hefore the hcaks ; valves closed, imllial sinus shalloiv, nhscure ; siphons short, 

 separate ; marine. Tertiary to Receiit. 



Pecchiolia Menegli. Sliell heavy ; beaks spirogyrate, distant ; sciilptiire radial. 

 Eocene ; Alabama. Mioceiie ; Europe. 

 Euciroa Dali. Recent, abyssal. 



The genera Verticordia Wood ; Trigonulina d'Orb. ; Haiiris Dali ; and (?) Allo- 

 pagus Stol. {Hippagus Desli., non Lea) are included linder the faniily Verticordiidae. 

 Tertiary and Recent. 



Family 13. Poromyacidae Dali. 



Shell rounded, nacreous and cellulo-crijstalline, granulär or smooth externally ; hinge 

 with^ obscure tuberdes in front of the resilium ; ligament external, opisthodetic ; resilium 

 sub-internal below 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 {Gymella, Psilomya Meek) (Fig. 747). Eqiiivalve, oval, thin, in- 

 flated, concentrically or 

 radially striated, gapiiig 

 and compressed behind ; 

 beaks prominent, in- 

 curved ; hinge with a 

 nymph and projecting 

 process on eacli side ; 

 ligament siinken, partly 

 external. Cretaceous. 



(?) Basterotia Mayer 

 {Eucharis Recliiz, non 

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

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



Poromija Forbes {Embla Loven). Ovate, plump, surface granulär ; pallial line 

 irregularly widened, not sinuate. Eocene and Recent. 



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

 line sinuate. Recent, abyssal. 



Cetomya, Getoconcha Dali (ßilenia Smith). Recent, abyssal. 



Fi(i, 747. 

 Liopistha frequens Zitt. Upper Cretaceous ; Gosau, Austria. Vi^ 



Family 14. Cuspidariidae Dali. 



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

 tions ; hinge edentulous or with sub-umbonal tubercula- 

 tion, sometimes buttressed ; 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 bciks 



when present. Jura to Recent. 



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

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



Fi(i. 748. 



Cusindaria cuspidata Olivi. 

 Miocene ; Baden, near Vienna. 



