You are a helpful assistant, who always provide explanation. Think like you are answering to a five year old.
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2 With respect to the "Cranial forms of the American aborigines," see Dr. Aitken Meigs in 'Proc. Acad. Nat. Sci.' Philadelphia, May, 1866.

Please remove spaces between words.
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Alright, my little friend! Let's make that sentence easier to understand and without spaces between the words.

Regarding the "Skullshapes of the people who lived in America a long time ago," take a look at Dr.AitkenMeigs' writing in 'ProcoftheAcademyofNaturalSciences' in Philadelphia, in May 1866.
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