Prosoma covered by large horseshoe-shaped carapace (convex dorsally)
2 eye pairs: large dorsolateral pair; small dorsomedial pair; both on carapace
Mouth is posterior to labrum (upper lip), with trisegmented chelicerae pair on each side
6pairs of cephalothoracic appendages
First four pairs, fifth pair, chilaria
Opisthosoma: unsegmented containing 6 short mobile spines at the posterior end, has 6 pairs of appendages with first pair forming the genital operculum
Telson: long triangular spine-like tail or caudal spine (not a true telson for horseshoe crabs (lacks anal opening)
Digestion
extracellular, intracellular within the hepatic caeca
Excretion & Osmoregulation
4 pairs of coxal glands- Common saclike chambers, coiled tubules, bladder, and excretory pore (located at base of last pair of walking legs)