266 Scientific Intelligence. 
species are entirely distinct. The remaining seven are ree pele 
Cheirurus, Ogygia, Ampyx, Ps silocephalus, and WViobe. The Pteropod 
l ; 
we know, first appear in the Tremadoe slates in Britain. Of the Trilo- 
bites, Agnostus princeps seems to be the fo species common to Lingula 
flags and Tremadoc slate, and of a tolerably aig list of bivalve _ 
shells ET Davisii and L. lepis are re only forms that ascend from 
the lower horizon. It was not till after the ea of Wales had been 
mapped that the existence of the Tremadoc slate as a recognizable sub- 
formation was suspected, for where almost all the rocks are slaty, an 
where there is no visible break in aiipareis minor chological distine- 
tions are eet of small value. AJ] known evidence e, however, tends 
to prove that in Wales the Tremadoc slate is a ea rt formation, and 
though searched for, none of its peculiar fossils have yet been found in 
Wales, except in certain spots in Merionethshire and Caernarvonshire. 
“Next come the Llandeilo and Bala beds, the prodigious development 
of life in which had no Leg ag in the older ne formations; and it is 
important to remember that the fossils of these strata are to a great ex- 
tent different generically, an a7 entirely apoaitioall from those 
known in the more ancient formation 
“ With respect, then, to Lingula, Poetic ce, and Llandeilo and Bala 
beds, taking into consideration the remarkable breaks in succession not 
only of species but of genera, together with various physical points of 
great significance, I have no doubt that actual unconformity exists in this 
part of the series, and het there is a necessary connexion between these 
facts. Indeed, this unconformity, if not seen, is, as already stated, nae 
inferred, for while in Merionethshire the Lingula flags are from 5,000 to 
6,000 feet thick, only 11 miles north, near Llanberris, their thickness is 
only 2,000 feet, this reduction having been produced proba ably by wncon- 
formable overlap. Close to —— Straits, if present at all, the Lingula 
beds are still thinner, and in Anglesey they are absent altogether, so that 
the Llandeilo and Bala beds lie. directly and, I believe, unconformably on 
Cambrian strata. To show that this is not a mere local accident, let me 
recall the circumstance that in Ireland and in Sutherlandshire the Lin- 
gula flags are also absent, and Llandeilo beds lie unconformably on Cam- 
brian grits and conglomera 
essor Ramsay aeons with a summary of his results with regard 
to the rest of the Silu 
The volume closes with an appendix on the fossils : Sena the plates 
of ong igi by the able paola 
é formation of the Dead Sea - by L. aera & me- 
moir on mie Dead Sea by Mr. Lartet closes with the following Senne 
soe — my geological study of the basin of the Dead Sea I a 
ink— 
(1.) That at the end of the Eocene period, and in consequence of an 
upward = (the date of the commencement of which cannot 
determi bed was protrud rresponding to the continen’ 
* Q) Bebe th pra igi MS: 
Sg ona this protrusion (even before the deposit of the Cretaceous 
disturbances had taken place i in the submarine beds, and a fissure 
