Sentence:  Dunn gives a key to a part of this group of "Eumeces", based upon the number of <WSD>nuchals</WSD>, placing the two American species (he does not consider "Eumeces altamirani" Dugès) in a group having 14-17 pairs of <WSD>nuchals</WSD>;.... 
Meaning of the word marked with <WSD> tags:  A neck scale, especially of a lizard.