BRacHIopoDA. 885 
Subgenus Eudesia, King. 1850. 
Synonym ; Plabellothyris, Deslongchamps, 1884. 
Biconvex shells, with dental plates, median dorsal septum, long 
recurved loop and sharply plicated exterior. 
Fias. 579, 580. Hudesia cardium, Lamarck (sp.). (DouviLLf.) 
(Type, Hudesia cardiwm, Lamarck (sp.). Jurassic.) 
Subgenus Orthotoma, Quenstedt. 1871. 
Shells small, subcircular, biconvex, smooth, with marginal 
median sinus on the brachial valve. Hinge-line straight. 
Fias. 581, 582. Orthotoma Heyseana, Dunker (sp.). (QUENSTEDT.) 
(Type, Orthotoma Heyseana, Dunker (sp.). Jurassic.) 
Subgenus Aulacothyris, Douvillé. 1880. 
Shells smooth, naviculoid in contour; brachial valve with a 
broad median sinus, pedicle-valve with conspicuous median ridge. 
Dental plates and dorsal median septum well developed. Loop 
long, fimbriate. 
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