Solution:Concept: The term "Limulus" means "king crab." Since 190 million years ago, Limulus has not changed. As a result, it is also referred to as a "living fossil." The four coxal glands, which are used for excretion, are present. The largest phylum of the animal kingdom is called Limulus.
The term Merostomata is an old lesson about creatures. It advanced within the early Cambrian (570 million a long time prior) and was a dominant life-form within the oceans and seas of the world until the Permian 310 million a long time back. Presently they are an awfully little bunch that comprises only 4 species in 3 genera and one arrange (or subclass) Xiphosura. Limulus may be a sort of horseshoe crab from subclass Xiphosura.
Hence, the correct answer is option 3.