Upon an examination of the accompanying illustration, it will be observed that the figure represented is that of a huge serpent or rattlesnake. A serpent was also the emblem or Totem of one of the tribes of the Mound Builders in Ohio, and there appear to be singular resemblances between the reptile carved in stone at Uxmal and that which is rudely made of earth and stones, and placed on high ground overlooking a valley in North America. Both reptiles have peculiarly large mouths, opened wide, ready to devour and swallow their prey or their enemies. It is perhaps not unreasonable to infer that the tribe who migrated from the north, conquered the unwarlike natives of Yucatan, raised the great pyramids, and built the temples in that region, were subsequently conquered by a more powerful tribe of the same race, also migrating from higher latitudes. The former tribe were forced to desert their buildings, and avoided slavery or extermination by escaping into the interior. The serpent stands out in bold relief. The whole of the façades of the nunnery are elaborately sculptured, and the mechanical abilities of the builders are well brought into notice. [Illustration: SERPENT EMBLEM, CASA DE LAS MONJAS.] As all investigations or theories respecting these architects and their works, depend greatly upon the conclusions that may be drawn from the evidence regarding the period when Uxmal was built, I directed my attention to certain points bearing upon this subject. Conjectures upon the origin and civilisation of the Indians must be influenced by what can be ascertained with respect to the probable dates when these religious buildings were constructed. It is to be seen in the Casa de las Monjas that there was a lavish use of ornamentation in stone. There is, throughout, a wealth of sculpture which is astonishing when it is remembered that the sculptors, as far as we know, had no proper implements to work with. Stone chisels and obsidian scrapers appear to be inadequate for the purpose.