AGE OF THE GASPE SANDSTONE 691 



The three said to be at all common are Cyrtina hamiltonensis, Nuculites 

 triqueter, and Tropidodiscus rotalinea. 



The fact that Cyrtina heteroclita, certainly a very closely related species, 

 ranges throughout the Lower and Middle Devonian of Europe diminishes the 

 value of Cyrtina hamiltonensis as witness of the Hamiltonian age of the 

 fauna. Cyrtma dalmani, which ranges lower than Oriskany, can not be 

 regarded as far removed from the Hamilton species. 



Nuculites triqueter can not be regarded as of much significance in making a 

 close identification of the fauna because of its wide range as a genus, and also 

 because of the exceedingly unsatisfactory characters it presents for specific 

 identification, as shown by the fact that Professor Hall in the elaborate volume 

 on the Lamellibranches of the Devonian of New York state in the preliminary 

 publication placed four figures of the plate illustrating the genus in the newly 

 described species N. nyssa, which in the final publication three years later he 

 listed as N. triqueter. This leaves only one dominant species of the fauna 

 positively correlating it with the Hamiltonian fauna. 



On the other hand, the following species of Oriskanian age are in the list : 

 Rensselwria oroides, Eatonia peculiaris, Leptocoelia flaoellites, Orthothetes 

 hecraftensis, Chonetes hudsonicus, Chonostrophia datcsoni, Chonostrophia com- 

 planata, and Phacops correlator, five of which are common or abundant spe- 

 cies in the York River fauna, and all of them are dominant Oriskany species. 

 Two other species, namely, Spirifer gaspensis and Leptostrophia blainvillei. 

 are also dominant species in these York River beds at Gaspe, and though not 

 reported outside of the eastern province are always found associated with 

 well known Oriskany species. Thus ten of the thirteen positively identified 

 species are dominant species in the particular fauna at Gaspe, and are also 

 dominant species in Oriskanian faunas wherever they occur. 



I can not escape the conviction that taking the list as given by Doctor 

 Clarke the dominant species of Oriskanian affinities present a much stronger 

 testimony as to the age of the fauna than do the Hamiltonian species, which 

 although greater in number of species are poorly represented in the fauna. 



But suppose we waive the differing values of the specific units in making up 

 the average, granting for the argument that the evidence is as strong for the 

 Hamiltonian as the Oriskanian elements of the fauna, is there any a priori 

 reason why we must assume that the Oriskanian element lived on in this one 

 locality until the Hamiltonian epoch? May not the same facts be interpreted 

 as indicating the early appearance in the Oriskanian epoch of traces of the 

 species which elsewhere did not appear till the Hamiltonian epoch? Not only 

 the intrinsic evidence of the fauna bears out this conclusion, but the geograph- 

 ical evidence supports the same view. 



The argument for Hamiltonian age is supported by the like association of 

 species in the upper of the two Saint Helens Island faunas, where are found 

 associated with species of Oriskany type other species of decided Hamiltonian 

 type. This argument, however, is offset by the fact that the Coblenzian and 

 other Lower Devonian faunas of Europe show a similar combination of species 

 which in North America are either characteristic Lower Helderberg-Oriskany 

 types or else are characteristic Middle Devonian types. If we suppose the 

 Gaspe basin to have been in open communication with the sea eastward, is it 



