The general problem is that while I got the testudine part, the line simply uses "dines" rather than "testudines"
testu, coming from the latin root testa meaning shell, is the important half of the word.
dines, meanwhile, was just the grammatical conjugation of the word? I tried to look up what that half means and couldn't find out back then, I was flipping through to see if I could find a connection to the word "undine" but that didn't pan out either. According to that page you linked, "testudo" is its singular and "testudines" is plural? (thanks for that, by the way)
Anyway, I wasn't really adamant about it because I was confused as to why he'd drop the part of the word that actually refers to the turtle shell and use the other half.