FAUNAL RELATIONSHIPS OF THE MEGANOS GROUP 127 
might be found in a group of beds belonging to one epoch of 
deposition. 
The foregoing remarks have especial application in connection 
with the faunas of the marine Eocene of the West Coast, where 
the larger part of the work of differentiating them remains to be 
done. Until very recently, one of the largest and most important 
breaks in the Tertiary of California, an unconformity in the Eocene 
deposits, was entirely overlooked, and a considerable part of the 
marine Eocene section of the state, as well as of Oregon and Wash- 
ington, has been described in a sequence the reverse of the fact. 
The fauna of Dr. R. E. Dickerson’s Siphonalia sutterensis 
zone, regarded by him as a part of the Ione formation in the foot- 
hills bordering the western front of the Sierra Nevadas, has been 
regarded until recently as coming from the uppermost Eocene 
of the West Coast. The beds of this horizon can be shown to 
belong well down in the Eocene section, and strata of the same 
age are found in the Coast ranges of California overlain uncon- 
formably by beds of Tejon age. The latter formerly were con- 
sidered to be the older. 
In a recent paper the writer has given a summary of his work’ 
on the Eocene in the vicinity of Mount Diablo, and has presented 
evidence to show that there are at least three major stratigraphic 
and faunal divisions in the Eocene of this region. Previously, 
only two such divisions had been recognized. The beds of the 
new division, to which the name Meganos Group was applied, 
formerly were considered a part of the Tejon. 
As will be brought out below, the writer is not the first to 
advocate a threefold division of the Eocene of the West Coast. 
The important fact to be remembered in this connection is that, 
while the fauna of the Meganos had been recognized by previous 
workers in this field as belonging to a distinct division of the 
Eocene, the Ione of Arnold and Hannibal and of Waring, the 
stratigraphic position of this horizon was wrongly determined 
and, instead of representing the uppermost Eocene of the West 
Coast, this division comes below the Tejon, and is the middle 
of the three Eocene divisions as now recognized. 
* Bruce L. Clark, “‘Meganos Group, a Newly Recognized Division in the Eocene 
of California,’ Bull. Geol. Soc. America, Vol. XXIX (10918), pp. 281-96. 
