246 
Mr. C. Lapwortli on the Geological 
very rapid. The new facts obtained, and the new views pro¬ 
mulgated, while they fully bear out my original generaliza¬ 
tions in all essentials, raising much that I regarded merely as 
a high probability almost to the rank of an absolute certainty, 
also enable me to add many illustrative details previously 
unknown. 
The evidences now at our command converge most dis¬ 
tinctly to the general conclusion that the various species, 
genera, and families of the Rhabdophora are quite as restricted 
in time as those of the more carefully studied Brachiopoda 
and Tribolita, and are consequently quite as reliable expo¬ 
nents of the systematic place of their containing beds. If, as 
I am inclined to believe, the Graptolites are destined to play 
among the Lower Palaeozoics the part tilled by the Ammonites 
among the Jurassic rocks, in fixing the minor divisions of the 
deeper-water beds, and in determining their parallelism in 
areas now geographically separated, the importance of the 
study of their geological distribution can hardly be over¬ 
estimated. At present our accumulated evidences are insuffi¬ 
cient to justify this broad generalization; and the combined 
results of the labours of many investigators are necessary 
before we can hope to arrive at a correct estimate of the office 
of the Graptolites in the Palaeontogeology of the Lower 
Palaeozoics. British geologists can no longer afford to neglect 
these ancient fossils, unless they are willing to be distanced 
by foreign investigators. Tolerably correct figures and de¬ 
scriptions of our commoner forms are now extant and are 
accessible to all. In the present article I will endeavour to 
summarize the main facts already determined—fixing our 
present point of departure in such a way that our future pro¬ 
gress may be easily estimated, and at the same time giving 
a general idea of the road upon which alone success is 
certain. 
(a) Geological Difficulties. 
Previous to 1873 the necessary data for a correct estimate 
of the range of even the main groups of the Rhabdophora were 
wholly wanting. We were fully aware of the presence of 
identical or representative species of Graptolithina in nume¬ 
rous localities, and in many different formations, on both sides 
of the Atlantic ; but the most erroneous views prevailed among 
geologists with respect to the proper parallelisms of all the 
more prolific of these Graptolite-bearing strata. To such an 
extent was this the case, that graptolitiferous beds which 
subsequent investigations have shown to be disjoined frag¬ 
ments of what was originally a single and continuous 
