130 PROF. GROOM ON THE CAMBRIAN AND | Feb. 1902, 
from which Dictyonema sociaie has been recorded, in the Tremadoc, 
in spite of the darker colour of the lower beds. 
It may be pointed out further that,in Shropshire and in Northern 
Herefordshire, the shales containing Dictyonema sociale lithologically 
resemble the Tremadoc Beds of Shropshire which do not contain 
this fossil. The Dictyonema-bearing shales of Malvern’ are for the 
most part of the same type, though some of the beds show a rather 
dark-grey colour. 
On the Continent most writers have followed Angelin, who placed 
the beds containing Dictyonema flabelliforme, EKichw., in his ‘ Regio 
Olenorum’*—the Olenus-shales of later authors. Linnarsson, who. 
first recognized the Dictyonema-shales as a distinct division,’ regarded 
them as constituting the uppermost division of the ‘ primordial 
fauna’; and most other Scandinavian geologists have adopted 
the same classification. Brogger, however, while sharing this. 
view, admitted that the Dictyonema-shales nught quite well have 
been grouped with the Ceratopyge-shales.* This course was, later, 
definitely advocated by Moberg,’ who has, moreover, recently offered 
fresh evidence in support of it." I understand that Senhor Delgado 
and Dr. Térnquist’ have also expressed themselves in favour of the 
same view. ‘The latter, indeed, adds that 
‘This proposition ... will, possibly, prove practicable in foreign countries. 
too.’ 
This suggestion appears to be borne out by the evidence adduced 
above from the British areas.” 
A few words with reference to the classification of the rest of the 
Tremadoc Beds may not be out of place here. In Britain the line 
between the Cambrian and Ordovician (or Lower Silurian) has 
commonly been drawn either between the Lower and Upper 
Tremadoc, or at the base of the Arenig. Mr. J. E. Marr, 
however, stated in 1883 ° that 
‘if a break is to be drawn at all on palxontological grounds, it should be 
drawn at the base of the Tremador, and not of the Arenig Series.’ 
1 Quart. Journ. Geol. Soc. vol. xxxiii (1877) p. 660. 
* « Paleeontologia Scandinavica’ p. ili (publ. 1854), 1878. 
’ Geol. Foren. Stockh. Forhandl, vol. 1i (1874-75) pp. 278, 274, & 282. 
4 «Die Silur. Etag. 2 & 3’ 1882, p. 156. 
> Sveriges Geol. Undersokn. ser. C, no. 109 (1890) pp. 1-9. 
6 Geol. Foren. Stockh. Forhandl. vol. xxii (1901) p. 528. 
7 Lunds Universitets Arsskrift, vol. xxxvii (1901) sect. ii, no. 5, p. 8. 
8 It may be remarked that Dictyonema sociale, Sait. is commonly regarded 
abroad as identical with D. jlabelliforme, Kichw. It is further to be noted that. 
in New Brunswick, while D. flabelliforme is found at what is apparently the 
same horizon as D. sociale and D. flabelliforme in Europe (that is, immediately 
above the zone ot Pe/‘ura and its associates), a variety also occurs in the 
Peltura-zone, and possibly as low down as the zone of Parabolina spinulosa, 
See G. F. Matthew, Canad. Ree. of Sci. vol. iv (1890-91) pp. 342 & 343. 
* *CQlassif. Cambr. & Silur. Rocks.’ Sedgw. Prize Hssay for 1882 (publ. 
1883) p. 23. 
