Both elk and deer antlers were used as tools, especially as projectile points. Some of the tools show evidence of being used as rubbing or grinding instruments. They were also used for chisels, but most items made of antler are difficult to interpret. The shells found at Aztalan were either used for decoration or as hoes. Most of the decorative shells seems to have come from the Gulf of Mexico.
Hoes tend to be the shells of river mussels.
Much of the other shell remains appear to have been discarded after the contents had been consumed. Source Barret, S. A. Ancient Aztalzn. Introduction to the Greenwood reprint by Rovert E. Ritzenthaler. Westport, Connecticut Greenwood Press.