59 



In a little ravine near the center of the vSection, a good 

 opportunity is afforded for the exploration of the Modio- 

 morpha subalata bed, which is twenty-five feet below the 

 Encrinal limestone. This bed appears near the center of the 

 cliff as a well-marked band one inch wide, whence it can be 

 traced in the bank of the ravine, to a little beyond a foot 

 bridge, where the layer produces a small fall or rapid in the 

 bed of the stream. Modiomorpha subalata (Conrad) is 

 extremely abundant, while the other fossils in this bed are 

 rare. M. subalata occurs in the beds above and below, but 

 nowhere in these shales is it so abundant, or so well pre- 

 served. The floor of the old Devonian sea must have been 

 thickly covered with these ancient mussels, which formed a 

 bed similar to those near our modern shores. The Trilobite 

 beds, and the calcareous layer above them, likewise appear 

 in the floor and banks of the little ravine. 



Beyond this ravine, the cliff rapidly increases in height, 

 until in its last third, it has a height of seventy-five feet or 

 more. It there forms one of the finest sections anvwhere to 



j 



be seen in this region. The perpendicular face of the cliff, the 

 projecting Encrinal limestone half way up, and the over- 

 hanging prismatic blocks of black Genesee shale on top, are 

 the most striking features, and all combine to make the 

 height of the cliff seem greater than it actually is. At the 

 northern end of the section the Trilobite layers appear on the 

 beach, forming a shelf at the water's edge. The middle bed 

 is highly fossiliferous, while the shale just below is full of 

 Streptelasma rectum Hall. The apparent northward dip 

 of the Trilobite beds is due to the direction in which the 

 section is cut, which in its lower part is more east and west 

 than north and south. 



Large slabs of Encrinal limestone occur on the beach, 

 containing Heliophvllum confluens Hall, several species of 

 Zaphrentis, and a large number of crinoid stems. Stropheo- 

 donta concava Hall is also common in the limestone. 



