TRANSACTION'S OF SECTION C. 657 



fish, was subsequently described by its discoverer as the type of a new genus, 

 under the name Diplasjns Acadica, though Mr. A. Smith Woodward claims that 

 it should be referred to Lankester's genus Cyathaspis. 



However this may be, in the Museum of the Geological Survey at Ottawa 

 there is a well-preserved fish tooth from the Upper Arisaig series at McDonald's 

 Brook, near Arisaig, N.S., collected by Mr. T. C. Weston in 1869. On the 

 ■evidence of large numbers of other kinds of fossils, the upper portion of the 

 * Arisaig series ' is still held to be of about the same age as the Lower Helderberg 

 group of the State of New York and the Ludlow group of England, but no 

 Devonian rocks are known to exist at jMcDonald's Brook. 



The tooth itself, which is not quite perfect at either end, is about eleven 

 millimetres in height, by about five in breadth at the base. It is conical, slightly 

 curved, and somewhat compressed, the outline of a transverse section a little 

 below the mid-height being elliptical. It is entirely covered with a thin coat of 

 •enamel, which is finely and longitudinally striated. 



Judging by its external characters, this specimen seems to be what is usually 

 •called a dendrodont tooth, and therefore probably that of a crossopterygian, per- 

 haps allied to Holoptychius, though its fore and aft edges are not trenchant. Only 

 •one specimen of it has been obtained, so that no thin sections of it have been made, 

 to show its microscopical structure. As it does not seem referable to any known 

 species, it may be convenient to call it provisionally Dendrodus Arisaigensis. 



If the limestones from which this tooth was collected are, as there is every 

 reason to believe that they are, of Silurian age, a second species can be added to 

 the vertebrate fauna of that system in Canada ; but if not, the tooth is still of 

 interest as indicating the possible existence of Devonian rocks at a locality where 

 £uch rocks have not previously been recognised. 



3. On some, new or hitherto little known Palceozoic Formations in 

 North-Eastern America. By H. M. Ami, M.A., F.G.S. 



Leaving out of consideration the Cambrian formations of the north-east part of 

 America, which have received careful attention at the hands of Dr. G. F. Matthew 

 and the late Mr. E. Billings, the author discusses the little-known formations or 

 faunas of Ordovician (Cambro-Silurian) age of New Brunswick and Nova Scotia. 

 This is followed by an attempt to subdivide the Silurian formations of the Acadian 

 provinces according to faunas, and by a correlation of these faunas with similar or 

 homotaxial faunas in Northern Europe. 



The subdivisions of the Devonian system are then considered, and their faunal 

 relations in the district in question, as well as to areas more to the south and west, 

 in the State of New York and in Ontario. 



The paper closes with a synoptical view of the phases which characterised the 

 Carboniferous period of North-Eastem America, a subject of special interest from 

 an economic as well as from a scientific standpoint. 



4. Some Characteristic Genera of the Cambrian. 

 By G. F. Matthew, LL.D., D.Sc, F.R.S.C. 



The paper gives in brief the history and use of several generic names and the 

 distribution of certain species to which they have been applied. These genera 

 have an important bearing on the antiquity of the Oleuellus Fauna — Bathyuriscus, 

 Meek, known as a Middle Cambrian genus in Montana and Nevada, occurs in the 

 OleneUus Fauna of Eastern North America, It is nearly allied to the following 

 genus— Bolickotnetopus, Angelin, of the Upper Paradoxides Beds of Sweden, is 

 found in beds of similar age in Eastern Canada. With it is associated Dorypyge, 

 Dames ( = Olenoides in part of Walcott), which is a Middle Cambrian genus in 

 Montana, and is found also in the Olenellus Fauna of Eastern North America. 

 Microdiscics, a genus of small trilobites, extending in Eastern Canada up to the 



1897, U U 



