976 PELECYPODA. [Eulamellibranchia. 



small, impressed ; escutcheon narrow, nearly linear, or absent : hinge- 

 plate broad and thick ; right valve with 2 anterior laterals and 4 

 cardinals, but the posterior cardinal, being extremely thin, is often 

 broken off, eroded, or obsolete ; left valve with 1 anterior lateral 

 and 3 cardinals ; valve-margins smooth ; pallia! sinus rather long 

 and usually acute, anterior lateral teeth nearly obsolete and mostly 

 simple ; sculpture generally of elegantly concentric grooves and inter- 

 spaces, sometimes raised into lamellae at the borders of the lunule 

 and escutcheon, crossed rarely with weak radial threads ; coloration 

 rarely disposed in patterns, and usually pale, many species being 

 white. The epidermis is nearly always thin and polished. 



Distribution. All seas. 



Fossil. Tertiary. 



Sect. 1. DOSINIA, s. str. 

 Type : D. africana, Hanley. 



Lunule small, impressed ; escutcheon narrow-elongate, flattish. 

 bordered on each side by a ridge or keel at which the concentric sculp- 

 ture tends to become lamellose ; lateral tooth small, smooth ; pallial 

 sinus angular, ascending, usually narrow and elongated ; valves 

 moderately convex. 



The escutcheon may be merely a flattening of the posterior dorsal 

 border, often unequal in the two valves, or it may be a well-defined 

 area bordered by distinct keel, more or less lamellose where the con- 

 centric sculpture intersects the carina. Between these types almost 

 continuous gradation may be traced. (Ball.) 



1. Dosinia lambata, Gould, 1850. Plate 62, fig. 1. 



Arthemis lambata, Gould, P. Bost, S.N.H., iii, 1850, 277 ; U.S. Expl. Ex p.. 

 xii, 422, atlas f. 536. Artemis lambata, Gould, Grit. List, 44. A. laudato., 

 Gould: Hutton, J. de Conch., xxvi, 49. A. lambata, Gould, M.N.Z.M.. 

 150. Dosinia limbata, Gould : Hutton, P.L.S. N.S.W., ix, 523. />. lam- 

 bata, Gould, ChaU. Rep., xiii, 151 ; Index, 89 ; Suter, T. N.Z.I., xxxix. 

 268. D. Carpenteri, Romer, Nov. Conch., Dosinia, 1862, 55, pi. 10, f. 2. 

 Artemis Carpenteri, Romer, Crit. List, 44 ; M.N.Z.M., 150. Cydinn 

 Kroyeri, Philippi, C.M.M., 72 ; not of Philippi. 



Shell rather small, lenticular, nearly circular, subequilateral. 

 brownish- white, very finely concentrically ribbed, somewhat shining. 

 Beaks somewhat anterior, elevated, acute, much inclined forward, 

 approximate. Anterior end somewhat compressed, regularly rounded, 

 the dorsal margin excavated in front of the beaks ; posterior end 

 broader, more elevated, dorsal slope a little arcuate, rapidly declivous ; 

 vi-ntral margin nearly circular, a little oblique. Lunule cordate, 

 short, distinctly marked. Escutcheon long and narrow, limited on 

 each side by an inconspicuous ridge. Sculpture consisting of very 

 fine and dense concentric stria?, some of the ridges rising into sharp 

 laminae at the extremities ; a faint granular appearance is produced 

 by microscopic radiating strife. Epidermis thin, somewhat shining. 



