YEARBOOK OF THE ASSOCIATION OF PACIFIC COAST GEOGRAPHERS VOL. IV.ifllfë Aboriginal Trade Routes for Sea Shells in the Southwest DONALD D BRAND University of New Mexico, Albuquerque Sea shells, when found in archaeologic ruins and middens of the Southwest , may provide data concerning prehistoric customs, techniques, and trade. This paper attempts to outline the methods and results of a study, into prehistoric trade routes in the Southwest, based upon the distribution of marine shells. The study was initiated by examining all possible literature on, and museum collections from, the area (arbitrarily taken as all of Arizona and New Mexico, most of Utah, and portions of adjacent entities) for mentions or exhibits of molluscan shells.1 The following difficulties were encountered almost immediately : 1.A great army of the reports on excavations failed to mention shells at all, or used such vague terms as "shells", "molluscs", "clams", "snails", and the like. At some sites, especially toward the northeastern interior, a lack or paucity of shell material might be expected, but such a condition on middle tributaries of the Colorado River is rather difficult to explain. Frobably, in most of such reports, neither the excavators nor the reporters were either interested or versed in malacology, and consequently failed to grasp the importance of preserving and recording all shell material—· both worked and unworked. Only in recent years has more than a paragraph or two been devoted to discussing the molluscan finds of an excavation .2 2.In the reports that made some pretence to listing the individual species , there was a wide variation in completeness, method, and accuracy of nomenclature. Some monographs gave only common names (such as white olivella, large Pacific clam, conch, whelk, cockle, scallop, and the like) which seldom could be narrowed down to the proper genus and practically never could be identified with a species. Quite often, seemingly, the excavators made their own field and museum identifications. It is possible that this procedure has conditioned the preponderance of Olivella, Glycy meris, Oliva, Conus, Haliotis, Cardittm , and Pectén identifications, since these seven most commonly mentioned genera probably are the seven easiest for the layman to recognize. Even when experts have been called in,3 there has been much discrepancy in the manner of citation and in the checking of obsolete or less valid synonyms. An example of this is one of the olives, which has been cited as: Oliva hiatula, Agaroma hiatula Gme lin, Agaronia testacea Lamarck, etc. One should not object, however, to many specific uncertainties in identification since most archaeologic shell material cannot be identified because of being (a) too altered by work (as is true of nearly all disc beads), (b) too fragmentary, or (c) too decayed. 3. Much of the archaeologic Southwest has not been worked, tither in time or in space. This is especially true of the so-called Develoj)niental or Pueblo I and II periods (roughly 600 to 950 A. D.) of "culture time", and of the Eastern Periphery , Middle Rio Grande, Chihuahua, and Sonora areas. Consequently, any (3) study in distributions must contain lamentable hiatuses. After determining what genera and species had been found (with subsidiary notes on use and culture period ), the next step was to establish the actual, most probable, or possible provenience of each genus and of ecah species. This was the most difficult portion of the study because of disagreements among conchologic authorities as to terminology, synonyms, and areal distribution.4 In general the areal disagreement was along lines unimportant for this study, e. g., whether a species was only in the Gulf of California or extended around to Magdalena Bay, or whether a species was found southward only to San Diego or extended to Cedros Island. In a few cases bad errors may have been introduced, as in Boekelman's identification (Gladwin , et al. : Excavations at Snaketown ) of a shell as Alectrion vibex Say (of Atlantic origin) when the shell probably was Nassarius (Alectrion , Nassa) tiarula Kiener (of Pacific origin). These two species are so similar that it might be said that they differ geographically rather than morphologically . Also, it is possible that Pectén gibbus var. irradians (identified by Wing for Nesbitt: Starkzveather...