9-P-8 or 9-P-6
The photo's caption is incorrect. Lt.Cmdr Spencer H. Warner is leading this flight of 18 planes from San Diego to Pearl Harbor on 1938-Jan-18/19. The flight broke a record: the largest formation of planes to cross an ocean. A correct reference can be found on p.429 in Chapter 4 of the Dictionary of American Naval Aviation Squadrons - Volume 2 (although it fails to mention the PBY-1s). A contemporaneous account can be found on p.155 of Joel C. Stovall's log book, with follow-ups on pp.152-154.
VP-9 is flying six PBY-1s (note the notched elevators). According to the Aircraft History Cards, they were assigned BuNos 0137, 0139-0142, and 0155 at the time.
VP-10 is flying twelve PBY-2s. (I can't see the top-side carburetor air-intakes of a PBY-3 on any of these planes.) They were assigned BuNos 0478-0489 at the time. Joel C. Stovall flew in 0489 (10-P-12). See page 46 of his log book.
Flt led by Capt Marc Mitscher, ComPatWing ONE
48 A/C - largest grp of A/C to fly 3000 miles
Fm: Capt C.W. Swanson, USN (Ret)
(Photo from the R.L.Lawson collection, courtesy of the Nat'l Museum of Naval Aviation)