modelgrafx@aol.com
Bob, In adults the males tail is considerably longer and fatter at the base. The females is fairly short and a little fat at the base near the vent. The females vent is very close to the edge of the shell whereas the males vent may extend nearly an inch past the edge of the shell. ( I just measured one of my adult males tail.) When looking at young dbt tails it has appeared to me that in the females tail it is a slightly incurving ‘ v ‘ where the males are a straight ‘ v ‘. As the males get older the vent moves farther away from the edge of the shell as the tail grows where the females vent does not. These are just my observations. How long is the shell length of your 1 1/2 year olds? I can add a tail photo of my year and 1/2 old females if you would like. Vickie