CLASR I 



PELECYPODA 



451 



Terquemia Täte {Garpenteria DesL). Shell witli a marginal ridge, f 

 right valve ; left valve fiatter, free. Trias and Lias. 



sessile by the 



Fig. 690. 



Exogyra columha Lam. Greensand (Ceno- 

 manian) ; Regensburg, Bavaria. 



Fig. 691. 



Exogyra flahelkitoi (Goldfuss). Cenomanian 

 Saint Paul Cloister, Egypt. 



Family 25. Eligmidae Gill. 



Shell thick, suh-equivalve, free lohen adult, resemhling Chalmasia in form, anteriorly 

 with an irregulär pedal gape ; edentulous, monomyarian, tüith the adductor seated on the 

 free extremity of a myophore projecting from the umhonal cavity, otherwise like the 

 Ostreidae. Upper Jura. 



Eligmus Desl. If the cliaracters of this genus liave been correctly interpreted, it 

 can hardly be retained in tlie Ostreidae. Fiirther investigation of tlie genns is 

 desirable. 



Superfamily 5. NAIADACEA Menke. 



Shell of varied form, normally equivalve and dimyarian ; rarely alate ; shell 

 suhstance nacreous and prismatic, loith a conspicuous epidermis ; area ohsßure er 

 amphidetic ; ligament parivincular, usually opisthodetic and external ; pallial lobes 

 usually free, except for an anal siphon, the pallial line simple; foot normally long, 

 compressed, heeled ; hyssus obsolete ; young usually with a distinct nepionic stage ; Station 

 usually fluviatile or lacustrine. 



Family 26. Oardiniidae Zittel. 



Shell equivalve, closed, with feehle concentric sculpture or smooth ; dentition schizodont 

 or ohscure ; ligament opisthodetic, external ; dimyarian, adductor scars suh-equal, pedal 

 scar feehle or invisihle ; Station marine or hrackish water. Devonian to Trias. 



Ämnigenia Hall. Devonian (Catskill) of North America, and Rhenish Priissia. 



Garhonicola M'Coy {Anthracosia King) (Fig. 692). Shell thin, oblong ; hinge 

 with a blimt elongated cardinal, and a feeble posterior lateral tooth upon a thickened 

 hinge plate. Common in the Goal Measures and estuarine Permian of Rnssia, also 

 America and Africa. 



Naiadites Dawson {Anthracoptera Salter). Shell modioliform, obliquely triangulär, 

 Avitli almost terminal beaks, straight hinge-line, striated hinge-plate, and superficially 

 marked with flat concentric lamellae. Goal Measures ; North Amei-ica and Europe. 



