NOTES FROM THE WEST OF IRELAND. 185 
immediately below the earthy layer before-mentioned. This 
earthy layer contains many AZ. zemoralis of a similar type to that 
at present existing elsewhere ; the shells are thin, light in texture, 
and retain much of their colouring, and obviously belong to a later 
epoch than the heavy specimens in the stratum below. As the 
shells from both strata weather out they are blown by the wind 
into the hollows of the sandhills, where they lie by hundreds 
intermingled together, but after a study of the separate strata 
there is little difficulty in distinguishing individuals belonging to 
the two epochs, by noting the material with which they are filled. 
The older shells are not only remarkable for their weight—which 
varies from 70 to 79 grains—and solidity, but also for their 
dimensions, the largest measuring 28 mills. in breadth, by 18 
mills. in height. The elevation of the spire varies considerably, 
some being much depressed. Several umbilicated specimens 
were found, and others had a thick, heavy, curiously constricted 
lip, folding inwards near the suture and forming a tooth-like 
protuberance; some of the heavier shells have also an ab- 
normally strong callus. Traces of the original banding occur in 
some few specimens, but they are mostly bleached pure white, 
and as a rule are very perfect, except that now and then an 
example occurs with a singular fracture, which consists in the 
breaking out of a small triangular portion of the lip near the 
suture. We are inclined to think that this is caused by the 
action of frost in expanding the damp material with which the 
shells are so tightly packed. A theory has been advanced by 
some of our friends, that the abnormal thickness of the shells is 
due to the gradual accretion of calcareous particles from the 
material in which they are embedded, and they point to the layers 
shown in a section of the shell as corroborative evidence of this. 
We cannot, however, bring ourselves to admit this theory of 
post-mortem thickening, for if such were the case we should 
expect the layers to be equally deposited on the outer side of 
the upper whorls, as well as on the inner side. But a section 
shows the colouring of the band on the upper whorl quite dis- 
