Unknown to us earlier were two springs near the Tank Site which possibly had some bearing on the original selection of this local. It was through Mr. Trujillo that these springs and several additional Topanga Culture sites were found. Mr. Trujillo, in his own way, had come to recognize these metate- and mano-bearing sites to be old and contrasted, as he says, "with the sites down along the creek where the soil is soft and dark with some sea shell and where mortars occur and the burials are all folded up." Such characteristics are typical of sites occurring in the protohistoric and historic period.
Probably most significant of this season's work was the partial excavation of LAn-2 located on the same ridge and about 350 yards below the Tank Site. Through our efforts here we were able to confirm the suspected stratigraphy in the Tank Site and, at least partly, define Phase II of the Topanga Culture. Of greatest contrast is the appearance of flexed burials and the exclusive occurrence of light projectile points. Although core and flake tools are still present, a definite shift occurs in the material from which they are made and the tools themselves do not dominate the cultural inventory.
From the Tank Site the artifact yield per cubic foot almost doubled that of the 1947 season. From the removal of approximately 2,496 cubic feet of mound we obtained 5,895 typable artifacts (all specimens and original data for 1947-1948 are now deposited in the Museum of Anthropology, University of California, Berkeley) or on the average of 2.3 artifacts per cubic foot of dirt removed. Compared to other California mounds, this figure is exceptionally high. Only in the Sacramento Valley among Late Horizon sites where baked clay objects were manufactured as a substitute for stone do figures run correspondingly as high, and even here one has to consider a single class of artifacts rather than a full range as expressed in the Tank Site. One explanation for the great increase for this season is that most of our excavations were conducted in the shallow part of the site (0 to 8 inches) where the bulk of the artifacts occurred.
Concerted excavation at the Tank Site was first carried on from June 19 to August 5, 1947. The immediate aim was to explore as fully as time permitted the nature and extent of the deposit. In the main, interest revolved on cutting long trenches, test pitting, and expanding in favorable areas. The compact nature of the soil and the heavy artifact yield retarded clearing. Nevertheless, some 5,000 cubic feet of mound earth was removed which bore an artifact content of one finished implement to every 1.5 cubic feet.