298 
The American Geologist. 
May, 1891 
I o\ i: 10. 
SEPTA. 
73. 
74. 
75. 
76. 
77. 
78. 
70. 
80. 
81. 
82. 
83. 
84. 
85. 
86. 
87. 
88. 
80. 
00. 
91. 
92. 
93. 
04. 
05. 
96. 
97. 
Rudimentary. 
Small one is sometimes 
observed. 
None indicated. 
May be present. 
Rudimentary. 
Large and smootb. Four principal ones stronger and 
projecting unite at center to form a cross. 
Numerous, generally extending to center and uniting, 
Confined to central core. Extend over expanded calic- 
inal margins as ruga'. 
Well developed, large, projecting, 
the center of calicinal pit. 
Extending nearly to 
Do not reach the outer wall ; equal or alternating. 
Equal, thick, straight and regularly radiate. Edges en 
tire. Extend nearly or quite to center. 
Fine, radiating septal stria? in the calyx. 
None indicated in orig- 
inal specimens. 
Quite distinct in sonic 
species, obsolete in 
others. 
None indicated or men- „ 
Rudimentary. At the outer edges they appear as low, 
linear crests, gradually vanishing towards the center. 
Rudimentary and frequently obsolete. May appear as 
rows of spines or as sharp crests, becoming rounded 
rugae at wall. 
tioned. 
One, more or less dis- 
tinct. 
Present as a groove on 
curved side. 
( me, quite distinct on the 
slightly curved side, 
Shallow, situated 
curved side. 
Septa are obsolete. 
Incompletely formed. 
Extend to center where they may or may not be twisted 
Stunted ; rows of spinulose forms or small closely com 
pressed lamellre. 
Incompletely developed. 
Rudimentary. 
Rudimentary. 
Rudimentary, but quite distinct. Low, spiny ridges lost 
beneath the vesicles towards the center. 
Diminished to slightly raised lengthened lines. Princi 
pal septum is on curved side, lateral ones at the angles. 
Numerous, thick, well developed, reaching center. Prin 
cipal septa are somewhat raised; situated at the mid- 
dle of each flat side. 
Principal septum may be somewhat projecting in the 
fovea. The others appear only as lengthened bands 
Usually small but well 
marked. 
One is indicated ; small. 
One, variable, usually 
well marked. 
( )ni', of variable dimen- 
sions. 
Thin, alternating. Primaries extend only to outer mar- 
Kin <>!' central area. Thin and flexuous in outer area. 
Alternating. Primaries extend only to outer margin of 
cellular structure. Secondaries are minute. 
Variable, alternating. Primaries extend only to outer 
margin of elevated central boss. Thin and flexuous in 
periphery. 
Alternating. Both orders extend towards center and 
coalesce, forming groups or fascicles. 
One present in large va- 
rieties. 
Lamellar. Extend from wall to center, uniting into fas 
| cicles. Not generally alternating. 
Well developed, alternating. Primaries extend only to 
One, well marked. < niter margin of central area. Secondaries shorter, thin 
| and disappearing 
