Tosefta zu Wajikra 3:18

What is the shankbone? It is taken from the socket and all the socket with it. The "shankbone" of the Temple is the "shankbone" of the countryside. What is the "cheek"? It is taken from the place of the slaughter and the entire place of the slaughter with it. The "maw" is as it implies. The fats that are on the maw are given to the Kohen. Said Rabbi Yehuda, the Kohanim used to behave generously, and they would give it [back] to the owners. The "shankbone" is the right shankbone. You may say, is it the right shankbone, or perhaps it is only the left shankbone? [But] behold, you may deduce, since the [breast and] thigh (Lev. 7:33-34) is a gift to the Kohen, and the shankbone is a gift to the Kohen, since the [gift of the breast and] thigh are only applicable to the right, the [gift of the] shankbone also is only applicable to the right. The thigh is from the joint and downward, the words of Rabbi Yehuda, and the Sages say, from the joint and upwards. What is the "breast"? Whatever faces the ground and upwards, until it reaches the neck, [and] downward until it reaches the belly. Two ribs should be cut off and given [to the Kohen] along with it (i.e., the breast). And these are the sacrificial parts [of the animal]: The two kidneys and the lobe of the liver and that which is attached to it. And these are the [sacrificial] fats: "The fat that covers the innards and all the fat that surrounds the innards" (Lev. 3:3, Fox tr.), those are the fats. [The fats] surrounding the rumen and all the fats that are on the small intestine, the words of Rabbi Yishmael. Rabbi Yishmael says, the fats that are on the maw, and the Sages did not agree with him. [With regard to the fat] that is on the loins between the sinews, one scrapes around it in every place that it is found and takes it away, the words of Rabbi Yosei HaGalili. Rabbi Yishmael says, the fat that is on the maw, which is spread out [and possesses] a membrane, and is [easily] peeled off, is forbidden. Rabbi Yehuda says, the membrane that is on the kidney is forbidden, and one is liable [for eating] it. The sinews that are in the kidneys and in [other] offerings are forbidden, but [bedi'eved] one is not liable for them.