114 NEW YORK STATE MUSEUM 



ous shale, which on Hthologic grounds is considered as Utica shale 

 (Perkins 1904, p. 117; 1916, p. 214).'' 



The Alburg shale contains an interesting combination of two of the 

 characteristic ostracods of the Canajoharie shale in the Mohawk 

 valley, namely, Primitiella unicornis and U 1 r ic h i a 

 b i V e r t e X , with Trenton fossils not observed in the Canajoharie 

 shale. The most common of these is Protozyga exigua, 

 a middle Trenton species so far known only from the Watertown- 

 Lowville region of New York. Also Ling u la trentonen- 

 s i s is a middle Trenton species, and O d o h' t o p I e u r a 

 t r e n t o n e n s i s is an element hitherto only known from the 

 Trenton of the Bay of Quinte in Ontario. It is thus seen that the 

 shale at Alburg forms a connecting link between the Canajoharie 

 shale and the northern Trenton. 



The shales at Cumberland Head near Plattsburg, were first noted 

 by White (1900, p. 460) who considers them as either "very high 

 Trenton or Utica " and cites a fauna, that is said to establish a con- 

 nection between those of New York and Canada. White points out 

 that similar rocks occur on Grand Isle, directly opposite Cumber- 

 land Head, and Gushing thinks that these are the transition beds 

 mentioned from there by Perkins (1902, p. 114). Gushing (1905, 

 pi. 13) has mapped these beds which he is inclined to consider as 

 passage beds from the Trenton to the Utica as " Cumberland Head 

 shale" and described them (ibid., p. 375) as consisting of blue-black 

 slaty limestones and calcareous shales, with some firmer limestone 

 bands. Ulrich, in the Revision, has correlated the Cumberland Head 

 shale with the lower and middle Trenton, or in a general way, with 

 the Canajoharie shale. 



The writer had the pleasure of spending, in 1919, a day on Cum- 

 berland Head under the competent guidance of Prof. G. H. Hudson 

 of Plattsburg, N. Y. It was seen that the Cumberland Head shales 

 are lithologically very different from the Canajoharie shale of the 

 Panton shore and the southern Ghamplain basin in general, for the 

 prevailing element is slaty limestone and graptolite shale was not 

 observed at all. The beds, as far as seen, are strangely barren in 

 fossils. The following forms were collected : 



" Professor Perkins is, however, aware of the fact that not all black shale 

 in Vermont is of Utica age, for he states (ibid, p. 208) : "In Vermont, as 

 in Canada, New York and elsewhere, there is in many of the exposures no 

 separation between the Trenton and the Utica for while the latter is almost 

 wholly shale and the former limestone, yet in places there is compact lime- 

 stone bearing Utica fossils and shale with Trenton fossils. Moreover in 

 some localities the Trenton passes into the Utica so far as the contained 

 fossils indicate." 



