They are called the obliques what you are describing.
However they are not what people here are refering too, it is the lower lats which are seperate from the obliques
Eternal Evil Soul, you have a wide lat spread. But like Deathmaggot said you need to bring out your lower lats more. But NOT the way Deatmaggot said, in fact I dont know how the hell he thinks that trains that area. (No offense Deathmaggot) Those exercises train your obliques, they have nothing to do with your back. It sounds like he made up a muscle group
To hit that area in your lats you need to do exercises like T-bar rows, reverse grip BB rows, close grip pull downs, reverse grip pulldowns, etc.. you get the idea. I almost developed that problem because I was doint to much overhand/width exercises. Also Deadlifts really help bring out that area as well, it will make your lower back look like its popping out.
i do a split of lat pull downs , seated cable rows,dumbell rows,bent over rows,t-bars and isolations movements on cable dumbell and machine and i also do hyper extention for back with 30,45,and 90 lbs plates and a lot of stuff but the thing is i dont diet or anything i love to lift and i am aspiring to become a bb soon my arms are smaller jst trying to get them bigger!