Reference for Gittin 71:10

מעיקרא במאי אפקעינהו בדיסקי:

But is not a mark enough? Did not Rab [sign by] drawing a fish and R. Hanina by drawing a palm-branch, R. Hisda with a Samek,<span class="x" onmousemove="('comment',' One letter of his Hebrew name. ');">⁹</span>

Jastrow