206 
ORIGIN OF LIFE IN AMERICA 
tation of some anatomical facts. Dr. von Ihering supports 
the opinions, upheld by almost all the prominent European 
conchologists, that the west American shells, which so greatly 
resemble the European Ariantas and Campylaeas, are really 
genetically connected with the latter. He even contends that 
no anatomical distinction worth mentioning exists between 
some of the American Epiphragmophoras and the European 
Arianta. Dr. Pilsbry, on the other hand, does not recognise 
any very intimate anatomical relationship between the Euro¬ 
pean and west American Helicidae, except in so far as he con¬ 
siders both to be branches of an ancient south Asiatic stock. 
As I shall explain later on, I concur with Dr. von Ihering, 
Dr. Sandberger, Professor Oppenheim, Professor Boettger and 
Dr. Kobelt in the opinion that many of the Antillean and 
west American forms are intimately related to extinct and 
recent European Helicidae. The great resemblance of the 
shells of Arianta and some of the Epiphragmophoras alone 
seem to imply a near relationship between them. 
The genera Ashmunella, Sonorella and Oreohelix are quite 
peculiar to south-western America, a large number of species 
having been described by Dr. Pilsbry and Mr. Ferris * in a 
series of articles contributed within the last few years to the 
Proceedings of the Academy of Natural Sciences of Phila¬ 
delphia. The same region contains many other distinct genera 
of land mollusks. The Urocoptidae, a family of snails some¬ 
what resembling the European Clausilia in shape, and having 
their headquarters in the Antilles, are represented by two 
genera, viz., Holospira and Berendtia, peculiar to south¬ 
western North America. 
Of some interest is the occurrence in southern Mexico, in 
lower California, and on the intervening islands, of many 
species of the large and ponderous genus Bulimulus. The 
difficulty of satisfactory identification unfortunately is such 
that there is little agreement among the various authorities as 
to the limits or range of species, nor is the nomenclature of 
these shells in a more satisfactory position. All the same 
as I shall mention later on, we can gather some useful hints 
from their distribution. 
* Pilsbry, H. A., and J. H. Ferris, “ Mollusca of the South-Western 
States.” 
