Ponderosa lemon
The ponderosa lemon originated in roughly 1887, and is believed to come from a chance seedling grown in Hagerstown, Maryland. It was later named and introduced to the nursery trade in 1900. Though often referred to as a cross between the lemon and citron, a recent genomic analysis showed it to solely contain pomelo ("Citrus maxima") and citron ("Citrus medica") DNA, perhaps being an F2 hybrid. Thus they cannot derive from true lemons, which have a mandarin orange component.
Palestinian sweet lime
Citrus limettioides, Palestinian sweet lime or Indian sweet lime or common sweet lime, alternatively considered a cultivar of Citrus × limon, "C." × "limon" 'Indian Lime', is a low acid lime that has been used in Israel for food, juice and rootstock. It is a member of the sweet limes. Like the Meyer lemon, it is the result of a cross between the citron ("Citrus medica") and a mandarin/pomelo hybrid distinct from sweet and sour oranges.