ADDITIONAL NOTES ON THE CAMBRIAN OF CAPE BRETON 
381 
Distribution of Acrothyra and Acrotreta in the Coldbrookian 
AND EtCHEMINIAN OF CaPE BrETON. 
These species and mutations are 
described in the following 
pages. 
W 
o 
o 
M 
C 
iJ 
O 
O 
Etcheminian. 
1 1 
2 1 
00 
a 
b 
c 
d 
•1 
h 
'1 
“ 
b 
c 
d\ 
e j 
/ 
A f’rr*!', hyrn. ciicrnn.ta. 
7^ 
18 
primal. 
SGra 
59 
6 
hn.rd n, . 
24 
* 
3 
A prnn.via, 
6 
m 
?i 
A primn 
1 
7 
A orM.ssn 
1 
? 1 
Acrotreta pn.pillata 
! 2 
A prima ^ 
1 
1 ? 
i 
A SD 
1 • • 
i 
i 
•-r' 
i 
1 
N. B. — The figures in the columns show the number of individual shells 
examined. The horizons where the types of these species are found are marked 
by heavy faced numbers. Only the ventral valves are recorded in this table. 
ACROTHYRA. 
For the characteristics of this genus see this Bulletin, Volume IV, page 303. 
Acrothyra signata, n. sp. Plate XIII, figs. 2 a-e. 
Valves corneous or calcareo-corneous, tumid, rather thick shelled. 
Ventral valve— Owd(\, pointed at the umbo, beak depressed and sides 
•compressed. Hinge larea oblique. Interior . — There is a strong 
narrow callus, one-third of the length of the valve, bounded by a 
raised ridge at the sides and in front ; at the front of this callus is an 
■oval pit, from which a groove runs backward nearly to the apex of the 
