MARCELLUS LIMESTONES OF LANCASTER 149 



accurately measured, and the entire thickness is probably 

 greater than 18 inches, since this corresponds to 30 inches of 

 the Plumbottom creek section, and the beds I and V at Cayuga 

 creek have suffered little if any diminution in thickness. Bed 

 V may be seen below the electric car bridge and just at the foot 

 of the dam which rests on it. At this place the entire thickness 

 of the bed is exposed. It seems to be made up of two layers 

 of concretions embedded in shale, the .lower 12, and the upper 

 6 inches in thickness. The middle part is compact and fossil- 

 iferous, the upper and lower parts more shaly and with fewer 

 fossils. Chonetes scitulus is the most common fossil, 

 while Ceratopora jacksoni and 0. dichotoma are 

 fairly abundant. 



Fragments from a bed similar to this were obtained from the 

 locality previously mentioned, near the corner of Buffum and 

 Seneca streets, Buffalo. They contain Chonetes m u c r o- 

 natus, C. scitulus, Strophalosia truncata, 

 Spirifer mucronatus and Cyphaspis eras- 

 p e d o t a . 



The following list offers a means of comparing fossils from 

 bed V, Plumbottom creek, with those from Cayuga creek. 



Plumbottom creek 

 Crinoid stems rr 



Chonetes mucronatus Hall rr 



C. scitulus Ball cc 



Strophalosia truncata (Hall) r 



Camarotoechia prolifica (?) Hall c 



Liorhynchus limitare (Vanuxem) rr 



Tropidoleptus carinatus (Conrad) r 



Spirifer (Martinia) subumbona (Hall) c 



S. mucronatus Conrad r 



Ambocoelia nana Grabau c 



Leptodesma marcellense Hall rr 



Phacops rana (Grem) rr 



Cryphaeus boothi Green o 



