TRIBE MACTRACEA. ate 
CRASSATELLA. 
Inequilateral, suborbicular or transverse, closed ; primary teeth. 
two, somewhat divergent, with a hollow at the side; no lateral 
teeth, nor obsolete ones ; ligament internal, inserted in a pit in 
each valve. 
C. Kinercoia. Lam. 1.—Sow. Gt. f. 2.—Reeve. Ic. f. 5. Ovate- 
orbicular, sub-gibbous ; yellowish-white under a brown epidermis, 
obsoletely rayed, with delicate transverse striz, the beaks plaited. 
3.—New Holland. 

M. Epuuis. Gray. Mag. N. H. 1837.—Macr. BE. Z. J. 5. 
p. 335. (young?) Ovate, thin, white, smooth, covered with a thin 
olive or reddish epidermis, forming two raised edges on the anterior 
slope: anterior slope white ; lateral teeth short, triangular. 2.. 24. 
—Port Famine. 
** * Anterior slope simple. 
M. Byronensis. Gray.—Beech. Z. t. 44. f. 11.  Ovate, 
slightly triangular, white, rather solid; lateral teeth short and 
rounded, (thinner when young). —S. America. 
M. Exausipa. Gray. in Mag. N. H. 1837. Ovate-oblong, 
white, rather thick ; umbones sub-anterior: lateral teeth short and 
thick, the posterior one sub-tubercular.— 8. America. 
M. Epuuis. Gray. Mag. N. H.1837.—Macrra E. King. 
Z. J. 5. Sub-triangular, tumid, smoothish, squalid fulvous ; 
inside white, the lateral teeth prominent. 2..25.—Port Famine. 
M. Lareratts. Gray.—Mactra L. Say. Jour. A. N.S. 
Phil. 2. p.309.— Gould. Mas. f. 34, 5.—Conr. Am. O.t. 14. f. 2. 
Triangular, very convex, nearly smooth ; lateral margins flattened, 
cordate, with a straight sometimes concave profile, one rounded at 
the tip, the other longer and less obtuse: umbo sub-central, pro- 
minent. }..43.—U. States. 
The shell, at present the sole representative of Mr. Gray’s genus 
GNATHODON, cannot strictly be included under any of the La- 
marckian genera, it comes tolerably close however to Mactra. 
GNATHODON. Gray. 
Sub-oval, equivalve, inequilateral, covered with an olive green 
cuticle, generally a little decorticated at the umbones ; a lateral and 
two cardinal teeth in one valve, two cardinal and two lateral in the 
other, the ligament in an intervening pit: sinus of the muscular 
scar small. 
G. Cungatus. Gray. Mag. Nat. 1837.—Sow. G.—Reeve. 
t. 43. 
Daz 
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