Where can I find a source for descriptive terminology of the nude
female form, as dealing with artistic and esthetic usage. In
particular I am looking for the name of the genetic trait for the
lower to mid back on females (and males) that is either a mostly flat
back or a back with a narrow valley along the spine created by extra
tissue on either side of the spine. I think there must be a source for
these traits and forms because of a question and answer in a back
issue of Playboy magazine. The question was something like: "What is
the name of the shape created at the top of a women's legs when she is
standing up straight with her legs together? (Where the thighs don't
meet and there is nothing between the thighs and the pubic area.) The
answer was "Delta of Venus". I imagine delta because of the triangular
type shape and Venus because of where the shape was and how it was
created. Is there a source terminology like this? And perhaps the
study of those shapes and forms?

As was under the impression that the "delta of Venus" is the female
pubic area itself, rather than the space below it that you describe".
If so, every woman has this feature, not just women of a particular
shape. It is, in any case, more a poetic (and erotic) phrase than the
sort of technical term you are seeking. It's most famous use was by
Anais Nin as the title of her book of erotic writings.

There are so many typographical errors in the above comment that I'm
going to redo it:

I was under the impression that the "delta of Venus" is the female
pubic area itself, rather than the space below it that you describe.
If so, every woman has this feature, not just women of a particular
shape. It is, in any case, more a poetic (and erotic) phrase than the
sort of technical term you are seeking. Its most famous use was by
Anais Nin as the title of her book of erotic writings.

You may be correct that it is the pubic area itself. Part of the
esthetics involved with the shape I am referring to is bound with
popular idealism of the nude female form. Along those lines the space
between their calves, knees thighs etc. I suppose what I should be
asking about is the science and study of the nude female form. Not
just size and shape but actual esthetic terminology. The study of the
lines of a woman, the shapes of her shoulders and neck, the curve of
her hip. The name of the characteristic of "kissable lips". Perhaps I
am asking too much. Perhaps this is an opportunity to create such
terminology and language.