6 



bulletin: museum of comparative zoology. 



The remaining eighty-five feet of the Trenton, (390-475 ft.) is a 

 dark, thickly bedded, impure Umestone with little shale, which on 

 weathering breaks down into a rubbly mass. Fossils are rather 

 common in places, but only on weathered surfaces. Strophomena 

 trilobata, Rafincsquina camerata, and R. deltoidea are the most common 

 and characteristic fossils, while Hormotoma trentonensls, Trochonema 

 umbilicatuni, and Streptelasma corniculum are other abundant species, 

 these latter forms being "recurrent" from the lower twenty feet of 

 the formation. 



The accompanying table shows the species found, and their vertical 

 distribution. 



