Reference for Keritot 49:11

אלא אי אמרת לאחר עריפה אמאי פטר ר"ש

is no slaughtering, while the Sages hold that ineffective slaughtering is regarded as slaughtering; but according to you who hold [it is forbidden] 'after the breaking of the neck', why does R'Simeon exempt him?

Jastrow