406 J. W. Dawson—Paleozoie Land Snails. 
rows of little pits which gradually pass into the continuous 
stria. The last whorl of the adult presents irregular lines of 
growth, instead of the regular microscopic ribs of the middle 
turns. Mature ovum membranous, or so slightly calcareous 
that it can be compressed without breaking: the embryo shel 
sometimes visible within. Length of adult shell rather less 
than 1 centimeter, breadth in middle 4 millimeters. 
Variety tenuistriata.a—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. 
te of preservation.—The shells are usually entire, but 
often somewhat flattened, and cracked or distorted in the pro- 
cess. Many fragments of shells, however, occur with the entire 
specimens, 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 structure, and the more perfect specimens 
found in the erect trees have a grayish brown color, like that of 
some modern Pape. 
The habitat of this species was in forests of the Coal-forma- 
tion period, composed of Sigillaria, Calamites, Lepidophloios and 
Ferns. The only known locality is the South Joggins, Nova 
Scotia. At this place the shells have been obtained in con- 
siderable numbers, though perfect specimens which can be dis- 
engaged from the matrix, are comparatively few. They have 
been found in erect Sigillarie 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 this locality for 
a very long time and must have survived many physical vicissi- 
tudes. 
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 
reptilian bones. The specimens obtained from this tree having 
been taken by Sir Charles to Cambridge and submitted to the 
late Prof. Jeffries Wyman, the shell in question was recognized 
by him and the late Dr. Gould, of Boston, asa land shell. It 
