Narcissus jonquilla is a well known species of daffodil and there is an entry for it in the database here:
Species Daffodil (Narcissus jonquilla)
The "simplex" part is a pseudoscientific made up name, which is pretty common in the nursery trade. They get plants that show some different trait(s) than standard plants so they create a name that helps them sell these "different" plants separately. But, the names aren't scientifically valid and they usually don't even meet the loosest definition of a cultivar either. The most common example of this is tacking "albus" or "alba" onto white flowered plants in species that usually produce colored flowers.
