PTNaz 57.d:37[2] :רישי<ה> דהן גבי עוקציה דהן עוקציה דהן גבי רישיה דהן‏ : the head of that (fish) is next to the tail of the other, and the tail of that (fish) is next to the head of the other
See the entire entry for ˁqwṣ n.m. spine, stinger