EXPLORATIONS IN WESTERN CANADA, ETC. 
125 
CENTKARCH1DJ5. 
The family Geiitrarchifl'je offers au apparent exception, since some of the gene'-aof 
this family liave much longer lins than the only Pacitic slope representative, as indi- 
cated by the following table: 
Atlantic slope genera triiliovi representatives on the I’acijic slope. 
Genera. 
Dorsal. 
Anal. 
Centraicluis 
XI or XJI, 12 
VII or YIII, 15. 
VI VIII, 15 
VI. 18. 
CbfEiiobi'vttus 
X, 9 or 10 
HI, 8 or 9. 
XI, 10 
V. 10. 
Einieacanthus 
IX or X,9-ll 
III-IV, 8-10. 
X, 10 
Ill, 12. 
Lepoinis - 
Xi 10-12 
Ill, 9-11. 
X. 13 
111,12. 
Bnt a comparison of ArcJioplites with its nearest Atlantic slope relative gives the 
following interesting results: 
Locality and siiecies. 
I)orsal. 
Anal. 
Pacific slope : 
Archojdites intermptus 
XIII, 10 
VII, 10 
Atlantic slope: 
AmblojditevS rupt^stris 
XI, 10 
VI, 10 
(living an increase of 2 spines in the dorsal and of 1 spine in the anal for the 
Pacific slope as compared with the nearest allied species, and an absolute gain of 1 
dorsal spine over all the other genera of this family. As the comparison ought obvi 
ously to be limited to those genera or closely related genera having representatives 
on both sides, the contrast (between Arc/; opii/c.9 and AmhlopUtes) is very striking. 
COTTIU.r. 
In this genus the dorsal and anal rays in different species are as follows: 
Sp( 2 cies. 
Pacific slo]ie. 
Species. 
Atlantic slope. 
Dorsal. 
Anal. 
Dorsal. 
Annl. 
VIII, IX, or X, 
IS 
VII, 16. 17 
124 
20. 
C. cojinatus 
VIII, 18 
14" 
VII, 18 
14 
\ni. 17 
13 
VIII, 17 
14 
VII, 19 
13 
A’lII 15 
11 
VI. is 
14 
VIII. 10 
12 
VIII, 10 
12 
VIII, 18 
15 
VII. i7 
12 
VIIl! 19 
U 
VIII, 17 
11 
VI VIII, 15 18 
12 
VIII 17 
12 
VIII 10 
11 
C. hoyi 
VI, 15 
11 
VIII--, 17i 
14 f 
VII. 17 
12-1- 
