CLASS 



PELECYPODA 



485 



Family 17. Lucinidae Fleming. 



SheU substance porcellanous or chalky, usually with inconspicuous or dehiscent 

 epidermisy rounded, variably sculptured ; valves equal^free, closedy with low, prosocoelous 



Fig. 790. 

 Lucina ( Miltha) gigantea üesh. Eocene (Calcaire Grossier) ; Grignon, near Paris. 2/3. 



heahs ; adductor and pedal scars adjacent or distinct, the lauer small ; anterior adductor 

 elongated, largehj within the pallial line, which is not sinuate ; area within the pallial 

 line often granulär or punctate ; cardinal area small, often deeply impressed ; ligament 

 and resilium suh-internal, set in a deep groove, but usually more or less visible externally ; 

 hinge-plate distinct ; lateral laminae distant from the cardinals, anterior and posterior 

 in the right, vjith corresponding sockets in the left valve ; cardinal teeth radial, formula 

 LlOlO 

 ROlOl' 



the posterior tooth larger and often bifid, but any or all of the teeth may be obsolete 



or absent. Silurian to Eecent. 



Paracyclas Hall. Eounded, thin-shelled, concentrically striated ; no luniile ; hinge 

 miknown. Devonian. 



Lucina Briig. (Figs. 790-793). Koimded, convex or lenticular, usually with a 



Fia. 791. 



Lucina {Myrteä) columbella Lani. Miocene ; 

 Steinabrunn, near Vienna. 



Lucina (Proltunna) prisca His. Silurian ; Gotlanil. 

 Internal nioiild (after Roemer). 



lunule ; with delicate, concentric, or more rarely radial sculpture ; dentition usually 

 normal, the laterals developed. Represented by upwai-ds of 300 fossil and 100 recent 

 species. (?) Silurian, Trias to Kecent. 



