Miscellaneous. 
455 
It will also be convenient to regard (with Professor Zittel) 
the first four families of the Rhabdophora as forming the arti¬ 
ficial division of the Monoprionida , and the last four as con¬ 
stituting the similar division of the Diprionida. 
Classification of the Lower Palceozoic Bocks .—The systems 
at present assigned to the Palaeozoic age fall into two main 
groups—an older group, including the Cambrian, Ordovician, 
and Silurian systems, and a younger group, including the 
Devonian, Carboniferous, and Permian. The period during 
which the former were deposited may be denominated the 
Loioer Palceozoic or Proterozoic Age ; that in which the latter 
were laid down may be called the Upper Palceozoic or Deute- 
rozoic. Broadly speaking, the Proterozoic rocks include all 
the sedimentary formations to which the name Silurian has 
at any time been applied by the most extreme adherents of 
the Murchisonian party in geology. With this extended 
interpretation the well-known generalization of Murchison 
that the Graptolites (Rhabdophora) are restricted to the 
Silurian system (Proterozoic period) still holds good. With 
one doubtful exception no Rhabdophora have hitherto been 
recorded from Deuterozoic rocks ; their highest known limit 
in Britain lies near the horizon of the Aymestry Limestone. 
Until very recently no British species had been recognized in 
rocks of earlier date than the Lower A renig of Ilicks; but 
the interesting researches of Dr. C. Callaway show that 
Rhabdophora are certainly present in the highest zones of the 
Shropshire Cambrian. The strata, therefore, that will neces¬ 
sarily be referred to in this connexion'are comprehended be¬ 
tween the base of the Upper Cambrian and the summit of the 
Silurian. Our accumulated knowledge of the sequence and 
fossils of the rocks in question is as yet too scanty to enable 
geologists to attempt more than their provisional correlation. 
The arrangement of the known Graptolite-bearing rocks 
which appears to myself most fully to harmonize our present 
evidences is that given in the accompanying Table. 
MISCELLANEOUS. 
The Cochineals of the Elm : a new Genus, Ritscmia pupifera. 
By M. Lichtenstein. 
The discovery of a new species of cochineal living on the elm 
would not he a proper subject for communication to the Academy 
of Sciences, if the curious form of this new comer and the peculiar 
circumstances of its development did not render it a very strongly 
