In Limulus polyphemus (Horseshoe Crabs) the excretory system includes four pairs of saccate nephridia, also referred to as coxal glands. These coxal glands are altered metanephridia that are similar to those found in crustaceans, other chelicerates, and some insects. The four coxal glands located on each part have the same duct that connects to a common nepridiopore that is located on the fifth cephalothoracic appendage. The coxal glands are positioned at the bases of the second through fifth cephalothoracic appendages but are very difficult to identify in adolescent organisms. In adult horseshoe crabs the coxal glands are bright red and easier to distinguish. Waste materials travel through the system of coxal glands and are excreted through the anus, which is located on the ventral side before the organism’s telson.