ACEPHALA. 431 
This shell was marked Feejee Islands, probably by some accident, 
as I doubt not, from its characteristics, that it came from Eastern 
Asia. 
It is allied to U. Murchisonianus, Lea, but is more widened and 
rounded posteriorly, is not sinuate at the ventral margin, is thinner 
and more compressed. 
Figures 540, 540, 540d, three views of the shell. 
Unio verecunpws (Gould). 
T. tenuis, inequilateralis, transversa, ovato-oblonga, convextuscula, luteo- 
olivacea; margine dorsali recto; margine ventral arcuato ; latere 
antico rotundato ; latere postico oblique rotundato ; apicibus prominuls, 
acutis, undulatis, erosis: cardo exilis ; dentibus tenuibus longitudinah- 
bus: margarita exsalmonaceo purpurea. 
_ Unio verecundus, Goutp; Proceed. Boston Soc. Nat. Hist., in. 295. 
Noy. 1850. Expedition Shells, 89. 
Suewt thin and fragile, transversely ovate, dorsal margin straight, 
slightly ascending; ventral margin very gently curved, nearly parallel 
with the dorsal; anterior end circularly curved, having the vestige of 
an angle as it joins the dorsal margin; posterior end without any 
abrupt angles; tip broadly rounded; margin above it oblique, gently 
curved ; beaks eroded, purplish, about two-fifths distant from the ante- 
rior end, slightly elevated, minutely undulated with oblique folds, 
some of which are zigzag; disk tumid, umbonal slopes obtusely 
rounded; epidermis thin, pale olive, with a tinge of red, generally 
smoothly adherent, except posteriorly. Nacre pale peach-blossom, 
darker posteriorly ; hinge very delicate; cardinal tooth single in each 
valve, elongated, nearly parallel with the margin; lateral tooth linear, 
delicate, straight, divided in the right valve ; muscular impression in- 
distinct ; pallial impression less so. 
Length an inch and three-fourths ; height an inch and an eighth ; 
breadth five-eighths of an inch. 
