660 Notices of Memoirs — The British Association. 



described, nineteen species are conspicuously mai'ked by a posterior 

 spiniform extension of the hinge-line, and form the section Spirifera. 

 ]n another group, where the spiniform extension is not conspicuous, 

 the umbo is remarkably prominent, and ten species are arranged 

 under the section Umbonata. In other forms, the anterior extremity 

 becomes nasute or rostrate, and seventeen species are placed under 

 the section Eostrata. Other forms are neaily flat and spreading, 

 ■with little or no extension of the hinge beyond the body of the shell, 

 and these forms are placed in the section Patidata. Other forms 

 have the hinge-line shorter than the width of the shell, the anterior 

 end rounded or truncate, and having the general form of Area. Of 

 these, six species are placed under the section Arcoidea. Still, a few 

 other forms have the aspect of 3Iytihis, and two species are placed 

 under the section Mytiloidea. Here we have a group of shells 

 among which we find no means of generic separation ; and yet 

 within its limits the species are developed in the direction of several 

 other genera, so far as regards form and other external characters. 

 The studies of this genus have been made from collections of many 

 hundreds of specimens with the result stated. An examination of a 

 more limited number of examples could easily have led to the 

 reference of some forms to the genus Mijtilus, some to Area, and 

 others to new and distinct genera. 



The forms of this genus, as at present limited, certainly exhibit 

 evidences of a most remarkable development in form and external 

 characters ; and are well worthy the study of the specialist in this 

 department of Palaeontology. 



3. — On the Coals of Canada. 

 By H. A. BuDDEN. 



COAL is widely distributed over the Dominion ; from the extreme 

 eastern point on the Atlantic, in the Island of Cape Breton, it 

 occurs, and through a portion of Nova Scotia and New Brunswick ; 

 from thence a wide blank exists, until about the ninety-seventh 

 parallel is reached; from it to the base of the Rocky Mountains 

 extensive fields are being developed ; it is also met with at various 

 points in British Columbia, but Vancouver Island, on the Pacific, 

 contains the most valuable deposits. 



Central Canada, although deprived of coal, is contiguous to the 

 immense fields of Pennsylvania, Ohio, &c., and through the medium 

 of the great lakes and the railways, is readily served at moderate cost. 



The principal fields are five in number. Those in Nova Scotia 

 are carefully described by Sir William Dawson, in his 'Acadian 

 Geology,' but among others. Sir Charles Lyell, Sir William Logan, 

 Brown, Hartley, Eobb and gentlemen in the service of the Geological 

 Survey of Canada, have given much attention to the subject. The 

 North-West fields have been surveyed partially by the Geological 

 Survey, Dr. George Dawson doing the principal work. Vancouver 

 Island and British Columbia are indebted to the late Mr. Richardson 

 and Dr. George Dawson for the results from their survey's; their 

 reports are to be found in the records of the Geological Survey. 



