heterocercal tail of fish.
"The Student's Elements of Geology"
Sir Charles Lyell
Tails of homocercal and heterocercal fish.
"The Student's Elements of Geology"
Sir Charles Lyell
This so called heterocercal tail is only known to exist, as a permanent adult feature, in the sturgeons of to-day.
"Louis Agassiz: His Life and Correspondence"
Louis Agassiz