Rangpur, sometimes called the rangpur lime, mandarin lime or lemandarin, is a hybrid between the mandarin orange and the citron.

It is a citrus fruit with a very acidic taste and an orange peel and flesh.

Rangpur was introduced into Florida in the late nineteenth century by Reasoner Brothers of Oneco, which obtained seed from northwestern India.

Rangpurs are highly acidic and can be used as a substitute for limes. However the name lime in connection with this fruit is misleading, because there are very few similarities between the rangpur and other fruits called limes.

More Info: en.wikipedia.org