Art. II. BoWnocker, Cor 7 tiferous Rocks of Ohio 29 
About two feet above the bone-bed at this point, the spe- 
cies L. rhomboidalis and ^S". ziczac are so abundant as to resem- 
ble a coquina. At Delaware there is a similar layer about 3 feet 
above the bottom of the quarry. If these two beds mark the 
same horizon, as the evidence indicates, the base of the Dela- 
ware quarries lies on or near the bone-bed. About 12 feet 
above the bone-bed is another zone of S. ziczac and L. rhom- 
boidalis. 
Near the summit of the strata at both Delaware and 
Marion lies a conspicuous bed of Tentaculites scalariformis . 
Often this shell is so abundant as to cover the surface of the 
rock. 
SANDUSKY. 
The formation found within or near this city belongs 
wholly above the bone-bed. The strata possess marked economic 
value, furnishing the city with high grade building stone. This 
retains the character which it possesses at Marion and Delaware. 
It is not usually worked to a depth exceeding 1 1 feet, and no 
observed exposures were found to a greater depth. According 
to the quarrymen it is not worked deeper because it becomes 
too thick bedded. This may mean that the beds just referred 
to belong below the bone-bed, for the layers found in this posi- 
tion are generally thick. Moreover no thick beds were found 
at any other localities above the bone-bed. The following spe- 
cies were collected : 
Spongia. Stromatopora sp. 
Anthozoa. Cyathophyllum halli. , Cystiphyllum ameri- 
canum. E. & H., Cystiphyllum ohioense. Nich., Favosites 
hemisphericus. Troost. , Zaphrentis prolifica. Bill. 
Brachiopoda. Atrypa aspera. Schloth., Atrypa reticularis. 
Linn., Athyris spiriferoides. Eaton., Chonetes mucronatus. M. 
& H., Chonetes yandellanus. H., Leptaena rhomboidalis. 
Wilck., Pentamerella arata. Con. , Schizophoria propinqua. H., 
Spirifera acuminata. Con., Spirifera maia. Bill. , Spirifera manni. 
H., Stropheodonta concava. H., Stropheodonta demissa. Con., 
Stropheodonta hemispherica. H., Stropheodonta perplana. 
Con. 
