How big is it? Do you know the approx age? I would say it's either a male Corydoras elegans (because it's pretty slender in shape), if it is an elegans then it is definitely male because of the pattern or a rather slender Corydoras trilineatus, with a lack of lines. I suppose it could be a julii due to that but i doubt it (theyre pretty rare). My bet is either C. trilineatus or male C. elegans. Dont bank on it though, i would definitely get more opinions.
edit: spelling
edit number 2 (lol): on second thoughts, I think its more likely C. trilineatus than C.elegans, but it could be either.
Yep it's a sodalis I have a reticulatus that might turn out sodalis dependant on his dorsal fin (he has a black splodge on his, but apparently sodalis can have clusters of stripes on theirs - so we'll see when he's bigger).