452 THE CANADIAN NATURALIST. [Vol. ix, 



within. Length of adult shell rather less than 1 centimeter, 

 breadth in middle 4 millimeters. 



Variety tenuistriata. — Along with the ordinary form there are 

 others of similar size and general structure, but with the apex 

 less obtuse and a somewhat greater tendency to diminish in 

 diameter in the later whorls. They have also the microscopic 

 ridges in the shell about half as far apart as those of the ordinary 

 form. This form I was at first disposed to regard as specifically 

 distinct, but there seems to be a gradual transition from one to 

 the other, and the two forms seem to accompany each other 

 throughout the entire range of the species. 



State of preservation. — The shells are usually entire, but often 

 somewhat flattened, and cracked or distorted in the process. 

 Many fragments of shells, however, occur with the entire speci- 

 mens, and some of these have a whitened or bleached appearance 

 like that of modern land shells after having been exposed to the 

 weather. In one layer I found impressions of several flattened 

 shells, the substance of the shell having been altogether removed. 

 Ordinarily the shell remains in such a state as to show its struc- 

 ture, and the more perfect specimens found in the erect trees 

 have a grayish brown color, like that of some modern Pupae. 



The habitat of this species was in forests of the Coal-forma- 

 tion period, composed of Sigillaria, CaJamites, Lepidop>hloios 

 and Ferns. The only known locality is the South Joggins, Nova 

 Scotia. At this place the shells have been obtained in consider- 

 able numbers, though perfect specimens which can be disengaged 

 from the matrix, are comparatively few. They have been found 

 in erect SigiUarice and also in a bed of shale. The lowest and 

 highest beds in which they occur are separated by 2,000 feet of 

 vertical thickness of strata, including no less than thirty-five 

 beds of coal and many underclays supporting erect trees, so that 

 the species must have inhabited the locality for a very long time 

 and must have survived many physical vicissitudes. 



The first specimen, which was also the first known Paleozoic 

 land shell, was found by Sir Charles Lyell and the writer in 

 1851, in breaking up the contents of an erect tree holding rep- 

 tilian bones. The specimens obtained from this tree having 

 been taken by Sir Charles to Cambridge and submitted to the 

 late Prof. Jeff"ries Wyman, the shell in question was recognized 

 by him and the late Dr. Gould, of Boston, as a land shell. It 

 was subsequently examined by M. Deshayes and Mr. Gwyn 



