Introduction 



nyms have not been listed except when there is 

 some confusion in the literature or recent change 

 in taxonomy. 



I had long felt that publication of photographs of 

 often fragmentary unworked shells in archaeological 

 field reports was an unnecessary expense, one which 

 I intended to avoid. However, in the course of 

 preparating this report, I realized that two factors 

 made such illustration strongly desirable. First, dur- 

 ing the continuous change and rearrangement which 

 characterizes all zoological taxonomy, generic and 

 specific terms rapidly become obsolete (e.g., of the 

 i8 Adantic molluscs listed on p. 6i of Kidder's 

 Artifacts of Uaxactun, ii of the names have become 

 obsolete since publication in 1947). Often, without 

 the actual specimen or a photograph at hand, it is 

 difficult to be sure to which taxon these obsolete 

 names refer. 



Second, because of their poor preservation and 

 sometimes fragmentary condition, identification of 

 archaeological shells is often extremely difficult and 

 errors are bound to occur. As reference collections 

 and knowledge of the local fauna increase, these 

 misidentifications may often be corrected, but only 

 if the originals or clear photographs are at hand. 

 For example, the large conch Strombus costatus is 

 extremely common on the north coast of Yucatan. 

 On the Caribbean coast of the peninsula, it is almost 

 entirely replaced by the larger and quite distinct 

 form S. gigas, which never appears on the north 

 coast. At Dzibilchaltun, 486 identifiable Strombus 

 shells and fragments were all of costatus, as would 

 be expected from gathering on the nearby coast. 

 ProskouriakofT (1962, pp. 384—85, figs. 43, 47), 

 however, reported the common large conch at Maya- 

 pan to be 5. gigas, which would imply a lack of 

 access to the neighboring north coast and unneces- 

 sary trade in bulk with the Caribbean coast over 200 

 miles away across Quintana Roo. This, as we shall 

 see below, would be in direct contradiction to much 

 other evidence now on hand. Without illustration, 

 the reader would be forced to accept this identifica- 

 tion, but with Proskouriakofl's excellent illustrations 

 the problem is quickly resolved. The specimens are 

 clearly the north coast costatus, not the east coast 

 gigas. 



For these reasons, we are illustrating our collec- 

 tion and also going a step further. On plates i— 21, 

 the archaeological specimens are designated by sin- 

 gle lowercase italic letters (a, b, c). Where these are 



too fragmentary to give a proper impression of the 

 shell, a complete specimen from our modern collec- 

 tion is added to the illustration beside the fragment 

 it amplifies. These modern shells are designated by 

 double lowercase italic letters {aa, bb, cc). 



Some of the fragments illustrated may seem to be 

 slim grounds for identification, but those published 

 here are reasonably certain. A small fragment of 

 hinge is usually sufficient for immediate identifica- 

 tion of pelecypod genus and often species, and final 

 identification can be often aided by a process of elim- 

 ination. For example, a small part of the ligamental 

 area of an ark shell identifies it as Noetia; there is 

 only one species of Noetia known in American At- 

 lantic waters; ergo our specimen is N. ponderosa. 

 Similarly, a relatively tiny fragment of gastropod 

 can often be precisely identified by comparison with 

 purposely broken modern specimens from the area. 

 We have been greatly helped by Harold and Emily 

 Yokes, invertebrate palaeontologists from Tulane 

 University, both specializing in Tertiary and Re- 

 cent Mollusca. Their job, like the archaeologist's, 

 has often required precise identification of fossil 

 material from small fragments, so our problem was 

 by no means new to them. They were kind enough 

 to spend many days in the field with us working 

 on the archaeological collections (in the course of 

 many weeks helping with our present project), and 

 have checked every identification presented in this 

 discussion. Without their help, we would have been 

 extremely hesitant to publish these pages. Thanks 

 are also due to Dr. Alan Solem of the Field Museum 

 of Natural History, who not only identified land 

 and freshwater molluscs, but was kind enough to 

 check in manuscript the corresponding two annexes 

 to the checklist. 



The modern distributions, unless otherwise noted, 

 are strictly peninsular, not implying presence or 

 absence in other adjacent or remote areas. They 

 reflect only the specimens in our own collection; we 

 have not yet collated the scattered peninsular report- 

 ings in malacological literature. As noted above, 

 our collection of larger species has been sufficiently 

 intensive to make most of the geographical listings 

 approximately correct. But we must bear in mind 

 that it is still only a sampling and that some species 

 surely have a larger range on the peninsula than we 

 have indicated. 



Although some recent sources have attempted 

 to distinguish between complete specimens and 



