Implied question: It could have taught a Nidmeh (a child that does not resemble its mother), for the Gemara explains the reason that we learn "Tachas-Tachas" from Kodshim!

Answer: Wherever it lists Kil'ayim, it normally skips Nidmeh, as if it is included in Kil'ayim, because it resembles it a little.

Remark: An animal whose legs were cut from the knee and above is among the 18 Tereifos;

There in Menachos (6a) we require three verses about Tereifah - one for a Tereifah from its mother's womb, which never had Sha'as ha'Kosher, one for a Tereifah that he was Makdish it after (it became Tereifah), and one for when he was Makdish it, and afterwards it became Tereifah;

[If its legs were cut] from the knee and below, it is considered that it can pass, since it did not become Tereifah.

Assertion: Everyone agrees to this Drashah, even the one who excludes Rove'a, Nirva, Muktzeh and Ne'evad from "Min ha'Behemah" and from "Min ha'Bakar", in Temurah (28a), like I explained (Chulin 23a DH Ki).

Observation: This Sugya is unlike Rav Chisda and Reish Lakish, like I explained above (42b DH Ki Pligi).

Explanation: The Gemara explains that this is 15 days, for Pros is an expression of half of the 30 days that we expound laws of Pesach before Pesach.

Ben Azai, who says Adar 29, argues with R. Akiva only about [the length of] the Adar next to Nisan. Ben Azai holds that it is always Chaser (29 days), and the time of the Goren is fixed. It is always Adar 29.

Inference: Erev Pesach is among the 15 days of Pros.

Support #1: Also in Rosh Hashanah (7a) it connotes so, that from the day of Purim we begin to expound [laws of Pesach] and not before, regarding "they testified that we may be Me'aber the year all of Adar";

They used to say until Purim, because we expound laws of Pesach 30 days before Pesach], and [if after expounding we are Me'aber the year and permit Chametz at the end of the 30 days], we they will come to disgrace [the Isur of] Chametz.

Inference: Since we consider from the day of Purim to be 30 days before Pesach, this shows that Erev Pesach is among the 30 days.

Support #2: Also R. Elazar and R. Shimon, who say below on Nisan 1, the Gemara explains that they hold like the opinion that says two weeks. This shows that Erev Pesach is among the count.

Question #1: In the words of R. Elazar and R. Shimon, it is taught "why didn't they say Tishrei 1? It is because it is Yom Tov, and one cannot tithe on Yom Tov. Therefore, they put it early on Elul 29";

According to letter of the law, it should be Tishrei 2, for the first day of Sukos is part of the count of two weeks! This is like Erev Pesach, for primarily they expound before the festival 30 days due to Korbanos, like it connotes in Avodah Zarah (5b);

It asks "why is the Isur [to do business with Nochrim] only three days before their festivals, and no more? A Beraisa teaches that we expound laws of Pesach [30 days before], and answers that for us, even a film on the eye disqualifies an animal for Hakravah, so 30 days are needed;

The primary expounding of laws of Pesach is due to [Korban] Pesach itself, which is slaughtered on Erev Pesach, and not due to the days of Pesach, for we learn from [30 days] in Pesachim (6b) because the Navi (Moshe) stood on Pesach Rishon and warned about Pesach Sheni, and the primary laws of Pesach Sheni are Shechitas ha'Pesach on Iyar 14 (30 days later).

The two weeks of R. Shimon ben Gamliel, we derive from that the Navi stood on Rosh Chodesh and warned about Pesach, and the primary laws of Pesach Mitzrayim was needed only for the day of Shechitas Pesach, for there were no other Korbanos.

Question #2: In Megilah (29b), it connotes that the two weeks of R. Shimon ben Gamliel, the day of action is not included;

There it establishes like him our Mishnah that on Adar 1 we announce about Shekalim, and it explains that since it was taught that on the 15th [of Adar] tables sit in the Medinah (outside the Mikdash), due to the tables we read early.

And the 30 days that we derive from that the Navi stood on Pesach Rishon and warned about Pesach Sheni, also it is without the day of action, for [if we would include the day of warning and the day of action,] there are 17 days [left] in Nisan and 14 days in Iyar, which are 31!

And from that Sugya in Megilah itself, it is hard to find 14 days without the day of action (he warned on Rosh Chodesh about the 14th of the month)!

Answer: Really, the day of action is not included. Chachamim did not distinguish between Pesach and Sukos. They followed the primary day of Yom Tov to begin the two weeks from the first of Tishrei, for on Yom Tov there are many Korbanos - Re'iyah, Chagigah and Simchah.

Implied question: The Navi stood on Rosh Chodesh and warned about Pesach, i.e. Shechitas Pesach on the 14th!

Answer: In any case, for all generations, for what there is to warn about Pesach, Chachamim were not concerned to rush (begin expounding) one day [earlier] for Pesach than for Sukos.

And regarding Shekalim, Chachamim fixed the time on Rosh Chodesh Adar, and they were not concerned to make it a day earlier before Rosh Chodesh, so there would be 30 full days, since the matter depends on Beis Din, to bring Temidim from the new Terumah (Shekalim), even though in our Mishnah here, we are meticulous to make the calculation exactly [15 days before Pesach] on Adar 29!

Support: Even though according to R. Akiva, sometimes Adar is full and sometimes it is Chaser, we never find that they changed the time of announcing Shekalim. Always on Adar 1 we announce about Shekalim.