26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I03 



satisfactory evidence is necessary to establish that fact. In some 

 ways this type of point is quite like others found under somewhat 

 similar circumstances, points also identified as Indeterminate Yuma, 

 that apparently have a late contemporaneity with Folsom types and 

 that persisted after the latter were no longer made (Roberts, 1940, 

 pp. 64-65). Hence it is possible that this early San Jon level dates 

 from the closing stages of the Folsom horizon, some 10,000 to 15,000 

 years ago. Geologic studies tend to substantiate such a conclusion, 

 although it must be regarded as tentative until more work has been 

 done on that particular phase of the problem. 



The next oldest remains comprise an assemblage of modern bison 

 and deer bones and points of the Collateral or Eden Valley Yuma 

 type. The significant factor in connection with this horizon is that 

 geologic evidence demonstrates that between it and the preceding 

 occupation there was a lengthy period of erosion followed by another 

 during which there was considerable deposition of new material. 

 The time lapse indicated is a relatively long one and during the 

 interval the large bison were replaced by a smaller species, the modern 

 buffalo. The cultural material from this level is unquestionably much 

 younger than that from the underlying one, a fact that has important 

 implications with respect to the status of different types of projectile 

 points in the Yuma series. There has been a general tendency to 

 regard all forms of the Yuma as more or less contemporaneous and 

 indicative of the same cultural age. If the San Jon point from the 

 oldest level is considered as an example of the Indeterminate Yuma, 

 a questionable classification discussed in the detailed consideration 

 in preceding pages, it is obvious that at least two of the Yuma forms 

 occurred in sequence and are characteristic of chronologically dif- 

 ferent stages. The present evidence tends to support a previous 

 suggestion to the effect that some of the generalized points regarded 

 as Indeterminate Yuma may represent the form out of which the 

 true Yuma developed. The definite break in occupation between the 

 two levels here, however, shows that the transition did not take place 

 in the San Jon district but if it actually did occur was accomplished 

 elsewhere. 



The break in occupancy evinced by the nature of the deposits is 

 of interest because it is in accord with indications noted in other 

 areas. For some as yet unexplained reason at most sites where traces 

 of the earliest hunting cultures now recognized are found there is a 

 definite hiatus between them and the following stages. Whether there 

 actually was an interval during which the regions where these mani- 



