Leptoplastus in the Acadian Cambrian Rocks. 485 
fauna (Peltura) or the fifth fauna. We, therefore, are still 
confined to the three countries of Scandinavia, Wales and 
Acadia as giving the most complete presentation of the 
sedimentation and life of the Cambrian period. Combining 
the ratios for these three countries we get the following 
result :—- 
General 
Norway. Wales. Acadia. Ratio. 
1 
Fifth fauna....Stage3a  1.2......1. ....1.1....1.1 U 
po SS i ere a | ee ae peots.-10 fe, ¢ (ae 
ete. 2... een ss Aj seeds, 300s 9 Sa 
Second “ .... “ led 23......2.5....15....211 4, Lower 
Sepa So (a been ee OL Oi; Cambrian. 
—_—— —_ en _ 
10.0 10.0 10.0 10.0 
These facts do not favor the separation of the Paradoxides 
beds from the Lower Cambrian, or their erection into a sepa- 
rate division as Middle Cambrian. If there is to be a Middle 
Cambrian it would rather seem that the Olenus fauna holds 
this position. But as has been shown the faunal relationship 
of the Olenus beds to those which follow them forbids their 
separation, just as in the Lower Cambrian a similarity in 
the forms correspondingly connects the Olenellus with the 
Paradoxides fauna, 
ON THE OCCURRENCE OF LEPTOPLASTUS IN THE 
ACADIAN CAMBRIAN ROCKS. 
By G. F. Marrunmw, M..\., F.R.S.C. 
It is somewhat singular that while species of Olenus have 
been found in Britain and elsewhere, the genus Leptoplastus, 
of which Angelin describes several species, appears to have 
been observed thus far only in Scandinavia.’ Angelin seems 
to have thought this genus so important that he made it 
the type of a family, Leptoplastide, in which he included 
Olenus, Parabolina, Peltura, Acerocare, Eurycare and 
Sphxrophthalmus. Leptoplastus may, perhaps, have been 
' The general average is taken for this portion. 
*I observe that Zittel (Traité de Palwontologie 1887, page 593,) 
mentions the occurrence of this genus in Great Britain, but does 
not give the source of bis information. 
