940 SCHISTODESMUS 
SCHISTODESMUS LAMPREYANUS (Baird and Adams). 
Shell triangular ovate, solid, subinflated to inflated, inequi- 
lateral; beaks moderately full and high; anterior end slightly, 
obliquely truncate above, rounded below; base rounded; out- 
line of dorsal slope lightly curved or straight; posterior ridge 
low, placed close to the post-dorsal edge of the shell, ending 
behind in a point about on the median line; surface having a 
series of strong, concentric ridges, which fade out just in 
front of the posterior ridge as in Venus paphia, each ridge is 
elevated into an elongated knob about the middle of the disk ; 
epidermis shining, apparently smooth but under a strong glass 
it is seen to be beautifully concentrically striate, yellowish- 
green or greenish-yellow with a few, elegant, broken, green 
rays, the old shells becoming brownish; pseudocardinals ele- 
vated, ragged; left valve with one high one under the beak; 
there is a compressed anterior tooth in front of this, close to 
the edge of the shell that connects with it and between them 
there is a deep pit filled with ragged matter; right valve with 
a somewhat double pseudocardinal in front of the beak; be- 
hind this there is a depressed shelf, and behind the shelf, under 
the beak the hinge plate is entirely cut off; laterals granular, 
that of the right valve partly dowble; beak cavities of the left 
valve deep; that of the right made shallow by the hiatus of 
the hinge plate; muscle scars small, impressed; callus behind 
the laterals small and distinct; nacre white, iridescent behind. 
Length 45, height 38, diam. 20 mm. 
Length 40, height 38, diam. 24 mm. 
Length 57, height 37, diam. 28 mm. 
China. 
Unio (Dysnomia) lampreyanus Barro and Apams, Proc. Zool. 
Soc. Lond., 1867, p. 491, pl. xxv1, figs. 2, 2a.—SOWERBY, 
Conch. jicon., XVI, 1868, pl. Lxxxvir, fig. 469—HeEuDE, 
Conch. Fluv. Nank., VII, 1883, pl. trx, figs. 114a, 114D. 
Margaren (Unio) lampreyvanus Lea, Syn., 1870, p. 30. 
Shistodesmus lampreyanus SIMPSON, Syn., 1900, p. 804. 
Schistodesmus iampreyanus Haas, Conch. Cab., Unio, 1912, 
pl. 31, figs. 1-4, 6. 
