222 THE CANADIAN NATURALIST. [Vol. vi. 



the species I have called Obohis Canadensis and 0. Galfensls. 

 For this group I would propose the name Obolellina. It 

 differs from Oholus ApoUinis in the form of the area of the ven- 

 tral valve, and in having a small pair of muscular impressions in 

 the dorsal valve, in front of the large central pair. In all three 

 of these sub genera, there are species which have the large muscu- 

 lar impressions of the ventral valve obliquely striated or grooved. 

 This seems to show that the muscles were not single but composed 

 of several bands. The three genera pass gradually into each 

 other, and yet I think some sort of a subdivision is required. It 

 seems almost absurd to place such shells as T. grandis and 0. 

 Canadensis in the same generic group. 



NATURAL HISTORY SOCIETY. 



FIELD DAY AT MONTARVILLE. 



The fourth of these social gatherings took place on Saturday, 

 June 3rd, the place selected being Montarville, or as it is com- 

 monly called, Boucherville Mountain. The weather being pro- 

 pitious, about one hundred persons assembled at the Bonaventure 

 Street Station, at 9 a.m., from whence they were conveyed by a 

 special train to Boucherville Station, wdiich was reached about 

 10.15. From this point vehicles of various descriptions conveyed 

 the excursionists to the grove near the lake on the grounds of 

 Madame Bruneau, the lady of the manor. When all were assem- 

 bled together, the President, Principal Dawson, stated that parties 

 would be formed to examine, respectively, the geological features, 

 the zoology, and the botany of the mountain. Principal Dawson, 

 Dr. T. Sterry Hunt, and Mr. A. R. C. Selwyn, undertook the 

 direction of the geological party ; Mr. Whiteaves was deputed to 

 lead the zoological expedition ; but as no botanist was forthcoming 

 to explain the points of interest in the various plants that might 

 be met with, Mr. S: J. Lyman volunteered to act as guide to those 

 who wished to ascend the mountain. Each party took a different 

 direction, with the understanding that all were to meet again at the 

 lake at 2 p.m. The results obtained by the geologists will be 

 found described in Dr. Hunt's and Principal Dawson's remarks 

 farther on. It may be mentioned, however, that on the way 

 Principal Dawson picked up two pieces of rock of Hudson River 



