I didn’t see this second post until after I had answered the first one. I am unfamiliar with this sy;mbol. I thought it might be an IPA symbol, but I don’t see it listed there. Does this textbook identify this symbol by name? If so, just use the words to identify it. When ths symbols appears in the text you can use an embedded TN at the location and enclose the name of this symbol in the TN. If you can’t find a name for the symbol, simply identify it as an unknown print symbol with an embedded TN.