92 es On the Starian System: 
*. posing on a stratum similar to that termed plastic clay, whilst this. 
latter is found at a short distance, towards the ] primary boundary. — 
I do not say that it may not occur beneath the fossiliferous beds — 
of the lower tertiary, although it has never been found in this rel- ‘ 
ative position, but in the vicinity ‘of Piscataway, Maryland, it fotr! 
poses on the latter strata, and forms the hills around, whilst the 
tertiary fossils are found in the beds of creeks and bottoms of ra- 
vines. ‘This clay is precisely similar to that around Baltimore, 
_ but unfortunately I could not find the lignite stratum, which char- 
* acterizes the plastic clay in so many places, over a great extent of. 
its course throughout the Union. But as that is a thin stratum, i. 
its absence must be expected in many localities of this formation. 
The evidence then, so far, is in favor of the opinion that this clay 
overlies the fousgiiteens strata of the lower tertiary, and, there- 
fore, does not exactly correspond in position to the plastic clay of 
England which underlies the beds of marine shells of the eocene 
period 5 still, they all belong to one era, and appear to have been 
deposited in estuaries or in fresh water in the beds of rivers near 
the sea. These remarks are made to call the attention of the 
state geologists to this subject, and it is hoped the question will 
soon be determined. 
ae 
+. 
Observations on the Genus Gnathodon, with description of $ ey, | 
new species. ee | 
Until recently, but a single species of this interesting venti 
was known to naturalists, the G. cuneata, (Gray,) an inhabitant 
of the estuaries of the Gulf of Mexico, and occurring in the up- 
_ per tertiary formation in the bank of the Potomac river in Mary- 
land, and on the Neuse river, North Carolina. The second species 
"described, was found in the high bank at Yorktown, Virginia, and 
_. is only known as a fossil. The third, which I now describe, is 2 
_recent species from Florida, which I owe to the kindness of Dr. 
Forman of Baltimore. 'The three species are very distinct, and 
the differences may be briefly stated in the following characters. 
: 1. G. cuneata. Anterior and posterior lateral teeth arched, 
.. “the latter being more than twice the length of the former. 
2. G. Grayi, (fossil.) Anterior tooth not greatly shorter than 
the en: both nearly straight. 
G. fleruosa. Lateral teeth not greatly differing in length, 
sa much shorter than in the preceding species, and _rectilineat- 
It is a smaller species than the others. 
