The first, ɤ, is the symbol for a back close-mid unrounded vowel, cardinal 15. This is the vowel heard in Mandarin Chinese 刻 kè [kɤ] ‘carve’.
The second, ɣ, is the symbol for a voiced velar fricative. This, or the corresponding approximant, is the consonant heard in the middle of Spanish fuego [ˈfweɣo] ‘fire’, Greek εγώ [eˈɣo] ‘I’, etc.
Confusion of these two symbols was something I often had to correct in authors’ manuscripts when I was the editor of the Journal of the International Phonetic Association. Since other copy editors may not have been so symbol-obsessed as me, the confusion is found uncorrected in quite a few printed books.
At its 1989 Kiel Convention the IPA discussed this issue. At the time the vowel symbol was usually printed with straight sides (although on the line, x-height), making it very similar to the consonant symbol (which descended through the line). See this scan of the IPA Principles booklet (1949 edition). The recommendation of the Kiel Convention was to change the sides into a curly “rams-horn” shape, which is what we use today.
If you have installed Doulos SIL, you should be able to see what they look like in a serifed font: