The Litumescens Fauna. — Clarke. 87 
and G-enesee county on the west ; they were the result of careful 
observ'^ations made over a period of several j'ears and part of the 
outcome of the work was a considerable increase in our knowledge 
of faunas which had hitherto been regarded as exceedingly meager 
and uninviting to either the geologist or palaeontologist. 
Since the publication of this paper the writer has taken every 
opportunity (always with the co-operation of his friend, Mr. D. D. 
Luther, of Naples,) to add to his representation and knowledge of 
these faunas. It has been inconvenient to undertake anj' systematic 
investigations in the country adjoining either on the east or west, 
but such desultory tours as have been made over the outcrops of 
these formations in the neighboring counties, lead to the conviction 
that certain important faunal characters are more positively de- 
veloped in the Ontario count}^ section than elsewhere, and that for 
the stud}" of these fossil faunas in their fullest development no 
area is as favorable as that which circumstances have made it con- 
venient to thoroughlj' investigate. 
The large amount of new and highlj' interesting material that 
has been obtained from these beds now makes the faunal lists of 
quite formidable size ; furthermore, the fossils, though of some- 
what rare occurrence, are not of such inferior preservation as one 
would infer from an inspection of the most extensive palaeozoic 
collections of the country, or from a few days' or weeks' collecting 
tours in the field ; they have, with patient work, proved moderately 
abundant and often of exquisite preservation ; indeed, we now 
possess series of many of the species, which afford the develop- 
mental stages from early age to maturit}-. It is the hope and 
purpose of the writer to eventually elaborate these interesting 
faunas and the growth-phases of their component species ; the ob- 
ject, of the present paper, however, is to indicate their quantiva- 
lence and time-values. 
Along the meridional section indicated, in a general sense that 
of Canandaigua lake, the (lenesee shales lie directly on the upper 
shales of the Hamilton group, the Tull}' limestone having thinned 
out and disappeared a few miles to the east. These shales have 
here essential!}- the same lithological cliaracters and variation as 
on the High Banks of the Genesee river, their separation from the 
underlying argillaceous Hamilton shales being rather more abrupt 
than is usual between formations of shal}' rocks following each 
other conformably. Toward their base the}' are somewhat areua- 
ceouSjbut rapidly become very l)ituniinous and heavy-bedded, these 
