84 THE CANADIAN NATURALIST. [Vol. X. 



The following are the species heretofore recognized : 



1. Nucleocrinus Verneidli, Corniferous Formation, Troost, 1841. 



2. " angularis, Corniferous Formation, Lyon, 1857. 



3. " Conradi, Upper Helderberg Formation, Hall, 



1862. 



4. " elegans, Hamilton Formation (also said to have 



been found as low as the Upper Silurian), 

 Conrad, 1842. 



5. " lucina, Hamilton Formation, Hall, 1862. 



6. " ■Kirkwoodensis, Sub-Carboniferous Formation, 



Shumard, 1863. 



NOTE ON THE COMPOSITION OF DAWSONITE. 



By B J. Harrington, B.A., Ph.D. 

 McGill College, Montreal. 



In connection with the discoveries of Dawsonite which have 

 been made at Pian Castagnaio in Tuscany,^ a few remarks on 

 the composition of this curious mineral may be deemed of interest. 

 It will be remembered that the specimens originally described in 

 1874 were from joints in a white feldspathic dyke cutting the 

 Trenton limestone near McGill College. f Since 1874 small quan- 

 tities of the mineral have been observed in the joints of several 

 other dykes in the same neighbourhood, and beautiful specimens 

 have been obtained at the Montreal reservoir, in what is probably 

 a continuation of the dyke near the college. In the latter in- 

 stance the Dawsonite is associated with calcite, dolomite, pyrite, 

 minute quantities of galena and occasionally of a black substance 

 rich in manganese. In all cases the mineral occurs in more or 

 less fibrous blades, which are often arranged in a radiated manner. 



* Two papers on the subject have appeared within the last few 

 months in the Bulletin of the Mineralogical Society of France (IV., 

 28 and 155), the first, entitled " Sur iin nouveau gisement de Daw- 

 sonite (hydrocarbonate d'aluminum et de sodium) et sur la formule 

 de ce mineral," by C. Friedel ; the second, " Sur le gisement de la 

 Dawsonite de Toscanne," by Maurice diaper. 



t Can. Nat. II. vn. 305. " Notes on Dawsonite, a new Carbonate." 



