Given how difficult and irregular the English is, I think you do an excellent job of conveying your needs. Which, by the way, we are more happy to help you with as best we can.
I can understand why you might feel this species is possibly divided up into subspecies. It is somewhat variable in colour. The crown, in particular, can vary in colour from a dirt brown through to yellowish brown through to a golden yellow or even white in particular individuals. The extent of the crown also varies, from two or three scales wide to five or six scales. It can extend from just past the eyes to well down the nape of the neck.
The diagnostic difference between it and its co-genitors, as mentioned, is that the crown does NOT cross the nape of the neck and join up. There are other variations but I shall leave it at that unless you want more information.
Blue