. 450 TRANS. OF THE ACAD. OF SCIENCE. 
alone. Where the general characters are so nearly alike 
as in the genus Polypora, it is often difficult to establish spe- 
cific differences among them; in many cases this can be at- 
tained only by accurate measurement and minuteness of de- 
tail in our specific descriptions. The P. incepta of Hall isa 
carinated species, but it has no line of tubercles on the lon- 
gitudinal rays. 
= ~ Portypora BiarMIcA, Keyserling. 
3x4 | 
This species is found in the Upper Archimedes meee 
of Chester, Illinois; at least, there are such slight ¢ 
between the specimens observed and that described in a te 
excellent description give i 
could find no grounds on hie to base a separation. The 
measurements given are precisely the same, and the fet iit 
ferences are, in the existence of four cells after b 
and as high as 
e. j 2 jarr é 
isa ‘Pleats rmian species, but is here foul below the Coal Meas 
ures of the Serboniferous series of the Western States.” 
fe | FENESTELLA BANYANA, D. SP: 
= x7. 
ryozoum msc a te Be widely ee fixed by mio} = 
Prt ag pedicles, me of which are single and 
Lon sapeadiaat + rays slender, Leones: witha harp 5° 
when much worn; but thicker, ro ee 3 a 
~~ tubercles _ slightly devise ews 
re perfect 
condition. 
Dis issepiments moderately thick, expanded wins 
_ the longitudinal rays, slightly depressed, one ke 
alf the size of the longitudinal 
the middle of the expansion, etait gases 
and about half one-fo as wide as the length ns alt 313% 2 
" Fenestrules more or less oval near base, oblong onl ra 7 
: 
; 
; 
: 
: 
; 
a 
4 
: 
| 
