78 THE NAUTILUS. 
path, to see him before treading upon him. Secondly, because if 
you carelessly step on the little round cactus so common in this 
region, the spines, if they do not puncture the sole of your shoe, will 
penetrate the upper leather more surely than needles. In the eyes 
of an eastern collector, accustomed to look for land shells in moist, 
shady places, it is not a promising country. There are no woods, 
except on the mountains, and few streams of water around whose 
banks mollusks might be expected. Yet there are shells all around. 
Find a cactus that is dead, and turn over its fallen leaves with a 
stout stick. Like the watermelon, a cactus seems to carry its own 
water, and under this moist, decaying mass the little Pupas may be 
found, and Helix Stearnsiana Gabb takes shelter fromthe sun. The 
night dews are heavy, and doubtless when darkness falls, the snails 
emerge from their hiding places, and browse around for food. 
Another favorite collecting ground is a pile of loose rocks; if on 
the south side of a hill, where the sun beats hottest, so much the 
better. Turn over every stone until the damp earth is reached, and 
your eyes will be gladdened by the sight of the elegant dark brown 
shiny Glyptostoma Newberryana W. G. B. Ifthe rocks are in the 
midst of shrubbery and herbage, the large beautifully banded Arianta 
tudiculata Binn. is likely to be found. Very rarely do any of these 
shells live on the shaded northern slopes, doubtless because where the 
ground is less heated during the day, less moisture is condensed at 
night. In this country, then, the collector truly earns his prizes by 
the sweat of his brow. 
One other land shell is the Succinea Oregonensis Lea, of a red- 
dish golden hue, found on the weedy river banks, and living only a 
little less in the water than its frequent companions Limneea 
Adelinz Tryon, and Physa Gabbii Tryon. These are the common 
shells of the open country, although far from numerous in-individuals, 
when one considers the hours of diligent labor necessary to procure 
a reasonable number. 
WHAT IS A SPECIES? 
BY CHARLES T. SIMPSON. 
In view of the practice of naming everything now-a-days by the 
so-called new school of conchologists, we may well ask the above 
question. Agassiz in classifiying animal life says, that “species are 
