AI

71

E..g

a

b

c

I.

A

f

d

e

(Coast)

(Gulf)

g

h

Fig.

I

The first method is not only more objective than-the second, but

holds well for hundreds of specimens examined from four large collections
containing shells from many localities, both fossil and modern. In deco-
rative beads or Kol-kol* strings from any one site, it is probable that

most of the shells will be readily identifiable as to the general area of
origin, while a few may be on the borderline as to the i"ridge"t character-
istics. It is always possible that a few fossil shells which could have
been made into beads had been found, or that trade routes were such that

a few shells came in from a distant area, or even that occasional mutations
occurred in the molluscs (although there is no evidence at present of vari-
ability approximating the shell characteristics of either opposite type).

As one typical kind of shell is found between Canada and Baja Cali-

fornia and another type is found from the northernmost part of the Gulf of
California to La Paz on the western side of the Gulf and to Acapulco on
the east coast of Mexico (O. anazora has even been reported from Western
Colombia, -and 0. undatella7from Panama), it would be interesting to know
if the tw types intergrade somewhere northwest of La Pazs where the ocean

temperature changes. If genetic drift or selective forces have acted upon
what had been one continuous population before the formation of the land
mass of Baja California and the isolation of the Gulf during the Miocene
Epoch, a less evolved type might be found. It seems more likely from

fossil evidence that a tropical type has spread into the new habitat of
the Gulf, while the less tropical type has remained on the coast. The

few Olivella species from the West Indies examined appear to be similar
in the two respects discussed here to the Gulf of California form, while
the Coast species are similar to a few from the Orient. Not many speci-
mens of fossil or modern Olivella from the Western Atlantic and Eastern
Pacific areas are availablIe"atpiesent.

* This term was used in historic times by several different groups of
California Indians, even non-coastal groups such as the Nisenan. See

Powers' Tribes of California, p. 3317, in U. So Geographical and ieolog-
ical Survey of the Rocky Mountain Region.  Contributions to North Ameri-

can Ethnology, Vol. III, Washington, 1877. Powers elaborates on the wide

use of shell money among the Nisenan, and lists values attached to certain
shells by the Indians, e.g., 14 yards of Kol'.kol, or 0. biplicata was
reportedly worth 14 dollars.

-g 31-