Although there is no NARA record or ADAH record of his service in the 42nd AL, however I have the widow's pension for him presented in 1899 that lists him as having served in that unit, but no other.
On 6 Oct. 1864 he is shown as enlisted in Dallas Co., by Lt. Barton in the 12th AL Inf. This is consistent with family records that he relocated to Cahaba, AL. He has a son that died as a child in Dec. 1865 that is buried at Cahaba. The comment on the Sept-Oct 1864 muster card is: "Recruit received from camp of instruction, Absent on sick furlough." His next sequential record in that unit is that he was admitted to CSA General Hospital in Charlottesville, VA on 8 Nov 1864 with a Parotid abscess. From there he was moved to Richmond Wayside and Receiving Hosp. and admitted 27 Nov 1864. This is the last record of him until he was granted a 30 day sick furlough by the Hospital examining board at Selma, AL on 11 Mar 1865. He was paroled at Selma 28 May 1865.
While it seems likely that Canterbury may have joined Co A 42nd Ala Inf, there is no record at present to support it. How common was it that a soldier from a disbanded unit (who was ~ 25 at the time of his enlistment) would be an inactive private citizen for a full 2.5 years afterwards? Although there is a possibility that he was ill (his later service record shows evidence of tuberculosis), there is no record to show that he was discharged for disability. Any thoughts?