MARCELLU/S LIMESTONES OF LANCASTER 143 



C 6 inches. The top of this bed is about 2 feet below the 

 lowest limestone layer. It is a calcareous shale much less fissile 

 than bed B. The rock recalls bed A in general appearance, but 

 is considerably darker and is highly fossiliferous. Nuculites 

 triqueter is the most common fossil. 



The following species were found here. 



Reptaria stolonifera Rolle rr 



Chonetes mucronatus Hall c 



Strophalosia truncata [Hall) . rr 



Liorhynchus limitare {Vanuxem) r 



Ambocoelia nana Gi'al)au r 



Nuculites nyssa Hall r 



N. triqueter Conrad cc 



Leptodesma marcellense Hall rr 



Lunulicardium fragile Hall o 



L. curtum Hall r 

 Aviculopecten exacutus \ffflZ? • rr 



Modiomorpha subalata {Conrad) r 



Pleurotomaria rugulata (?) Hall rr 



Styliolina fissurella {Hall) r 



Orthoceras subulatum Hall c 



Goniatites vanuxemi (?) Hall c 



Isochilina (?) fabacea Jmies r 



D 12 inches. The lower part of bed D is similar to the preced- 

 ing, but is more fissile and contains Liorhynchus limi- 

 tare (a rare form in bed C) as the most abundant fossil. The 

 fissility becomes more pronounced till, in the upper part of the 

 bed, the rock breaks into extremely thin laminae with their sur- 

 faces crowded with the flattened shells of Liorhynchus 

 limitare and scattered individuals of Strophalosia 

 truncata. In certain of these upper layers the latter condi- 

 tion becomes reversed and the S-trophalosia is the more abundant 

 form, the shells overlapping one another. The individuals of 

 both species are here exceptionally large. This layer is not well 

 exposed in the bed of Plumbottom creek but may be seen in 

 situ in places along the bank. 



