a Srauta question

[Madhav Deshpande]

Dear Indologists,
        I am reading a text which refers to a Kalpa text in 16 adhyAyas
beginning with the words athaitasya samAmnAyasya.  As far as I know, this
is the first sUtra of the ASvalAyana-Srauta-sUtra, but this sutra has only
12 adhyAyas.  Does anyone know of another SrautasUtra which begins with
the same words and has sixteen adhyAyas?
        All the best,
                                        Madhav Deshpande