Variations of External Appearance and In- 
ternal Characters of Spirifer Cameratus 
“Morton. 
Contributions from Paleontological Laboratory, No. 30. 
BY. J; W.. BEEDE: 
With Plate VI. 
GENERAL DESCRIPTION. 
Shell medium to large in size, greatest convexity back of middle, 
variable in outline from sub-semicircular to trigonal; anterior mar- 
gin sharply rounded to truncate-sinuate, lateral margins slightly 
curved to nearly straight, pointing outward and “backward to the 
ears; hinge line equalling the greatest width of the shell, some- 
times prolonged into attenuate ears; cardinal area broad, extending 
to extremity of hinge line; foramen broadly triangular and nearly 
equilateral, partly closed in upper part by pseudodeltidium; beak 
high, prominent, somewhat recurved over cardinal area which is 
sometimes slightly arched; mesial sinus prominent, beginning at 
beak and broadening and deepening until the front margin is 
reached; fold of dorsal valve to correspond and beak of the same 
moderately rounded beneath that of the other valve; interior of 
ventral vaive marked by a sub-elliptical muscular impression in the 
vicinity of the beak, posterior end of this depression extending to 
the hinge line or beyond, bisected by an indistinct, mesial ridge, 
radiating from which are small indistinct ridges for the attachment 
of the muscles. The cardinal area projects, leaving a large space 
beneath; the shell is here well pitted for attachments; asmall tooth 
and depression are developed on the inner corners of the cardinal 
area. Shell of dorsal valve thin, muscular marking indistinct, 
hinge line at beak broadly and shallowly arched, one prominent 
socket on each side of arch, for teeth of other valve, two small 
elevations in the center for attachments. The exterior markings of 
the shell consist of rather large, bifurcating, radiating striz or 
costz, almost always fasciculated, covering the entire shell to the 
(103) KAN. UNIV. QUAR., VOL. VII, NO. 2, APRIL. 1898, SERIES A. 
