128 THE NAUTILUS. 
Smooth, olive green; sometimes radiate with pale yellow; 
others are olive-brown. The beaks are seldom eroded, being 
thickened there by flexuous wrinkles—remarkable because the 
rest of the shell is smooth. 
Nacre bluish. The cardinal tooth is compressed, and de- 
current in shape. 
Being thin, it is crenulate instead of being furrowed (other 
members of the subgenus have them furrowed); truncature ob- 
lique, convex. 
Lateral tooth thin. Muscle scars lightly impressed, confluent 
behind. 
A smali species, at most one and a half inches in altitude. 
(The members of the sub-genus described just previously by 
Rafinesque are among the largest of the Ohio Naiades. ) 
Altitude 3 of length; diameter 7. 
Rare in the Ohio, but common in the Kentucky and ad- 
jacent ‘‘ petites rivieres.’’ 
While to the writer the above description can be mistaken for nothing 
else than the Symphynota compressa Lea, further evidence seems neces- 
sary, as Lea quotes one of his friends to the effect that ‘‘ rt equally 
applies to wis.”’ 
Luckily there remains further evidence which we may ad- 
duce. Rafinesque, as is well known, divided the Naiades into 
numerous Genera. These divisions being founded upon the 
more evident features of the shell, it follows therefore that the 
contained species of any Genus would naturally sustain a general 
outward resemblance to each other. 
Rafinesque described this species under the name of Unio 
(Elliptio) viridis. The Elliptio contained the Unio nigra; Unio 
purpureus, Say; Unio crassa, Say, and a few other shells, all 
having a general outward similitude, and in such an assemblage the 
Symphynota compressa finds congenial associates. 
Rafinesque moreover mentions the fact that the ‘‘ Unio 
( Elliptio) leptodon and Unio (Elliptio) fragilis’’ also ‘‘ resemble’’ 
the viridis (with some others). The reader can easily select speci- 
mens of the two species mentioned, which resemble the Sym- 
phynota compressa to a remarkable extent—differing, however (as 
Rafinesque observes), in their teeth. 
