104 The American Oeologist Ftb. isoo. 
filled in with refuse two years ago and the snails were hiiried 
and are now only known to have ever occurred here from the 
specimens in the various cabinets in this city. 
In both the latter cases man's agency was at work in the 
extinction of species, but in the case of the shells in the 
Tuscarawas river man played no part. 
These instances may serve to remind us that in palaeontol- 
ogy as at present we need not look for cataclysms and convul- 
sions to account for the extinction of species, but must often 
attribute them to local changes, slight but sufficient, in the 
keen struggle for existence, to handicap the losers in the race. 
AN ATTEMPT TO EXPLAIN GLACIAL LUNOID FURROWS. 
By A. S. Packard, Providence, R. I. 
In hisadmiral)le report on "the rock-scorings of the great 
ice invasions" in the seventh report of the U. S. geological sur- 
vey Prof. T. C. Chamberlin draws attention to the subject 
of lunoid furrows, and rejects my explanation of the cause. It 
may be said that the first observer to call attention to these 
crescentic ice-engravings was Dr. John Delaski, of Maine, (I 
think Falmouth or Yarmouth) who saw them on Mt. Desert, 
and described them in the American Journal of Science for 
Sept., 1863, (2d Ser. xxxvi. 275). 
Having observed these ice-marks,at various places in Switz- 
erland the past summer, and not having been satisfied with 
my former explanation, I venture to suggest what may seem 
to be a more reasonable one. It also appears that the lunoid 
furrows are apparently the same as Prof. Chamberlin's "cres- 
centic gouges." 
I first observed them at the Gletschergarten of Lucerne, 
where they are not, however, very well marked, as the rock is 
a limestone, and not favorable for their best development. 
The photograph Avhich I obtained quite closely resembles Prof. 
Chamberlins' fig. 33 of the disruptive gouges in sandstone, 
at Amherst, Ohio. Besides the gouges or true lunoid furrows, 
the limestone rock at Lucerne was in places more or less 
scaled off irregularly, as if the result of pressure. The surface 
was inclined, the ice having been apparently forced locally 
uphill. Afterwards in walking up the Grimsel Pass, these 
lunoid gouges were observed in abundance on the granite spur 
