Question

How do you make this into a parrell sentence? Thank you

Palm readers examine lines on the palm, fingers and their lengths, and the prominence of the mounts.

Answer 1

Any series (three or more items) needs to have all its parts in the same structure -- all nouns; all adjectives; all nouns with one adjective; all present participles; etc.

Here's what you have:

Palm readers examine lines

on the palm,
fingers and their lengths,
prominence of the mounts

You could say that each of the items in the series includes a noun, they are not parallel. Here's why:

~~on the palm = noun in prepositional phrase
~~fingers and their lengths = 2 nouns, one with a modifier
~~prominence of the mounts = noun with a prepositional phrase (including a 2nd noun) modifying it

How can you re-write this sentence so that all elements of the series are phrased with the same construction?

Read this carefully before you decide:
http://grammar.ccc.commnet.edu/grammar/parallelism.htm

Answer 2

I left an important word out!

" ... includes a noun, <b>but</b> they are not parallel."