310 



Moorea bicorndta. Ulrich. (Fig. 253.) (Joum. Cin. 

 Soc. Nat. Hist., Vol. XIII., p. 191, PI. XVI.) 



Distinguishing Characters. — Sub-ob- 

 long, elliptical, rather strongly con- 

 vex valves; strongly rounded, nearly 

 equal ends; straight hinge line occu- 

 pying the two central fourths of the 

 length; gently convex ventral edge; 

 two blunt spines near anterior 

 margin ; prominent posterior eres- 

 centic ridge. 

 Found in the ''Hamilton group, at Eighteen Mile Creek, 

 N. Y." (Ulrich, type.) 



Fig. 253. Moorea bicornuta. 

 Side, end, and ventral views 

 of a right valve, x 20 (after 

 Ulrich). 



Genus BAIRDIA. McCoy. 



[Ety. : Proper name.] 

 (1846: Synop. Carb. Foss. Ireland, p. 164.) 



Carapace varying in form from broadly triangular to nar- 

 rowly elongate sub-triangular: extremities more or less 

 acute; surface smooth, finely punctate or setiferous. Left 

 valve overlapping the right. Interior of marginal borders, 

 except on the dorsal edge, cased with a narrow lamelliform 

 plate, as in Cypris, except frequenth^ for a slight fold or 

 notch at the angles of the hinge line. 



Bairdia legemixoides. Ulrich. (Fig. 254.) 



Cin. Soc. Nat. Hist., Vol. 

 197, PI. XVII.) 



Distinguishing ( 1 invaders. — Acu- 

 minate sub-equal ends, the posterior a 

 little more blunt; dorsal edge arched 

 in the middle, concave on the sides; 

 regularly curving ventral border ; 

 thick overlapping edge of left valve; 

 J^s^J"^ 1 JSSS faintly marked central spot of right 



and anterior views of a perfect i 



carapace, x 20 (after Ulrich I. ValVC 



(Journ. 



XIII.. p. 



