﻿JV. S. Shaler — Geology of Cobscooh Bay District, Me. 55 



Spirifer cyclopterus ? 

 " octocostatus. 

 Rhynchonella mutabilis. 



" abrnpta. 



" vellicata, var. 



" formosa. 



Rhychonella aequivalvis, var. 

 Rennselaeria allied to R. ovalis (doubtful). 

 Leptocoelia allied to L. fimbriata. 



" u L. concava. 



Atrypa reticularis (extremely abundant.) 

 Orthis pedunculosa, var. 

 • " planoconvexa, var. 

 Strophodonta planulata, var. 



" Beckii, var. 



Trematospira allied to T. Deweyi. 



Articulata. 

 Dalmanites closely allied to D. micrurus. 

 Tentaculites irregularis, var. 



In this and the following lists of species no revision of the 

 generic and specific names has been attempted. 



The thirty-three species of fossils which are named in the 

 preceding list, have been in the main determined from casts of 

 the exterior or interior, of the shells or other hard parts ; this 

 being the form in which the remains are commonly preserved 

 in the beds of this locality. The species from the equivalent 

 New York strata have generally been described and figured 

 from specimens which show the substance of the hard parts. 

 Any one who has undertaken identifications under these cir- 

 cumstances, must have remarked the difficulties involved in 

 such comparisons. Despite these hindrances to complete deter- 

 mination, the identification may perhaps be taken as sufficiently 

 accurate to serve the needs of the problem in hand. 



There can be little doubt that these species prove the beds 

 from which they came to be, in a general way, the equivalent 

 to the Lower Helderberg group of New York, but it does not 

 seem possible, at least at present, to refer the deposit to any 

 particular division of that series of beds. It should also be 

 noticed that there remain at least twenty species of fossils from 

 this locality, which are as yet unidentified many of which may 

 hereafter be found to belong to other geological horizons ; more- 

 over nothing like a complete collection of the fossils contained 

 in the deposit has yet been secured. 



Although the species given in the ubove list are in most 

 cases closely related to the forms to which they have been 

 referred, it must not, for the reason before given, be assumed 



