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889 



TERTIARY FAUNA OF FLORIDA 



Genus RBSANIA Gray, Jan., 1853. 

 Type li. lanccolata Gray + I'anganclla {Taylori) Gray, June, 1853 + Myomacira C. Mayer, 

 1867 -J- Laminarui C. Mayer, 1867. 



Shell inequilateral, thin, compressed, lanceolate, smooth, with a conspicu- 

 ous epidernns; dorsal areas obscure; beaks very low, adjacent, somewhat 

 posterior; pallial sinus short, broad, gapes conspicuous; ligament small, short, 

 lanceolate, not set off from the pit by a shelly ridge ; chondrophore large, 

 oblique, posteriorly depressed below the hinge-plate and resting on a radial 

 thickened rib, which extends from the beaks towards the base behind the 

 posterior adductor ; a second rib of the same sort reinforces the valve behind 

 the anterior adductor; resilium homogeneous, dental armature concentrated; 

 left cardinal strong, prominent, petaloid, with a thin posterior accessory lamella, 

 which, with posterior arm of the tooth, projects slightly over the pit; a short, 

 thin, well-elevated lateral tooth on each side of the beak ; a small but deep 

 lunular inflection of the anterior dorsal margin ; right cardinal low, wide, the 

 anterior arm superposed on the ventral lamina ; the anterior dorsal lamina very 

 small between the arm of the cardinal and the lunular inflection ; posterior 

 arm of the cardinal projecting a little over the pit ; the posterior laminae small 

 but distinct. The gills are discontinuous on one side, and the whole mantle 

 edge free between the adductors. A single species is known from New 

 Zealand. 



Genus DARINA Gray, 1853. 

 Type D. solcnoidcs King (not Ltitraria solenoidcs Lam.) + D. Kingii Fischer. 



Shell inequilateral, thin, siliquiform, smooth, with a conspicuous epidermis ; 

 dorsal areas not differentiated ; beaks posterior, adjacent, inconspicuous ; pallial 

 sinus deep; shell gaping at both ends; ligament lanceolate, very short and 

 narrow but deep, not separated from the pit by any lamina ; chondrophore 

 large, nearly vertical, depressed below the hinge-plate, and resting on a 

 thickened, obscurely ray-like portion of the valve ; resilium composed of two 

 lateral horny parts, adhereht to a medial calcified layer, which separates them 

 like an ossiculum ; dental armature feeble, concentrated ; left cardinal petaloid, 

 small ; the posterior arm projecting entirely across the upper part of the pit, 

 attended by a posterior accessory lamella, nearly of equal size, which over- 

 hangs the hinder border of the pit; anterior arm of the left cardinal larger, 

 walling the anterior border of the pit; a low, obscure lateral tooth on each 

 side of the beak in this valve ; right cardinal obscure, the anterior arm coal- 

 escent with the anterior ventral lamina, the posterior excessively thin and 



