220 TRANS. OF THE ACAD. OF SCIENCE. 
sinus and plications of the opposite valve; beak smaller and 
curved beneath that of the i valve. 
while the reverse is true in others e sinus varies i Wi 
and depth, and is marked with trot two to six plications; all 
the plications are usually more strongly marked in very 
gibbous specimens. 
Missouri State collection, and or Hawn’s, from the Upper 
Coal Measures of Missouri and K. T 
To show the variable form of this species the measurements 
of two specimens are given 
No. 1—Length, 0.48; breadth; 0.44; thickness, 0.40. 
‘oo sen 0 45: breadth, 0 05 iceor ag! ie! sian atee 
are Tike’ Camarophori. Schlotheimi, ee Rus, 
volt it)! aie they are not identical” 
_ Rerzia PUNCTILIFERA, Shumard. 
apne a oie 
"sinus, ‘which phe Rea fom the front nearly 
re small, tr 
third the ae of pha she 
the Feclepen and the sides dis 
ow 
SaaS bs Beale much pro. 
