﻿56 J¥. S. Shaler — Geology of CobseooJc Bay District \ Me. 



that complete specific identities have been proved ; that degree 

 of accuracy in the determination cannot be secured until much 

 more extensive comparisons are made. 



It should be noticed that there are many genera of fossils 

 which are commonly represented in the deposits of Lower Hel- 

 derberg age, which have not as yet been found in this series of 

 rocks. So far the abundant collections have shown no Ling- 

 ulas, no distinct Meristas, no Nucleospiras, no Trematospiras, 

 no Leptsenas of the L. depressa type and very few species of 

 the genus Orthis. There is scarcely a trace of corals or cri- 

 noids ; no Bryozoa have been found. 



The next locality of importance is that near Dent's Point, at 

 the head of what is locally known as Leighton's Cove. The 

 physical character of the rocks differs considerably from that 

 of the Orange Bay deposits, before described. The Leighton's 

 Cove series consists in the main of shales generally thin-bedded 

 and containing but little lime. About two hundred feet in 

 thickness of beds is exposed, but of this only the upper half is 

 fossiliferous. The fossils are well preserved, but have been 

 subjected to a considerable distortion from pressure ; the elon- 

 gation being in a general northeast and southwest direction. 

 Thirty species have been found in these beds, of which the 

 following have been approximately determined. 



List of Species. 



Dalmanites limulurus. Clinton. 



Beyrichia symmetrica. Niagara. 



Orthoceras imbricatum. 



Orthis allied to O. elegantula ) as usual these two forms blend 



" O. hybrida \ together. Niagara. 



Atrypa cuneata, var. Niagara. 

 Chonetes allied to C. cornuta, but much larger ami with finer 



ridges. Clinton. 

 Orbicula squamiformis, var. Niagara. 

 Lingula oblata. Clinton. 

 Avicula allied to A. textilis. Lower Helderberg. 



" emacerata. Niagara. 



" rhomboidea. Clinton. 

 Modiolopsis sublatus. Niagara. 



" ovatus, var. Clinton. 

 Orthonota curta, var. " 



Cyclonema ventricosa. " 



Murchisonia subulata. " 



The greater part of these species are represented by abun- 

 dant but poorly preserved specimens. Although the identifi- 

 cations are not perfectly satisfactory, they serve to show the 

 relation of these beds to the horizons of the Clinton and 



