They are quite rare I'd say. Even when you do find them they are rarely labeled Rostrata. Their markings, like yoyos, kubotai, and historanica change as they grow. Here is a link to a profile. Yours seems to be about the same in pattern development as the last picture on the page.
At the bottom of it there is also a link to another page showing how their patterns change as they grow.
At the bottom of it there is also a link to another page showing how their patterns change as they grow.
