No, I wasn't an English major. Sorry about that. They are marines but I suspect that if the photo was taken on Guam, it wasn't during the initial assault wave.
Generally, when you see pictures of marines in combat conditions, you may see M1 carbines but there is usually an M1 Garand somewhere in the photo. In this photo, I see nothing but M1 carbines. Every man has a carbine. That is one thing that makes me suspect a support/artillery unit.
While many marines wore the P42 camo utilities, especially the camo helmet covers, my understanding is that many if not most still wore the 1941 pattern cotton herringbone utilities. I don't know who got what and when but in the photo, you can just make out that the bed rolls are camo. Perhaps they had camo helmet covers packed away. I wouldn't want to go into combat with one of those shiny helmets glistening in the sun... but many did.
Wow, that’s a lot of new information for me. Great stuff!
You have a sharp eye, my friend. Good stuff.
All things considered it seems to me the photo is more likely to be of a training exercise on Guadalcanal than an actual landing operation on Guam. That would mean the Times caption is incorrect. If they had the photo on hand since May they knew it was incorrect when they ran it. Hard to believe.