CRABS, ETC. 93 
Order VIII. Merostomata.—The king or horseshoe 
crabs (Fig. 108) attain a length of two feet, and have a 
wide geographical range. The last segment of the ab- 
Fic. 108.—Horseshoe crab. A, Limulus Moluccanus, dorsal view. B, 
Limulus rotundicauda, ventral view (after Milne-Edwards): @, ante- 
rior; 4, middle division of the body; c, telson; ¢@, subfrontal area; ¢, 
antennules ; 7, antenne; g, operculum; 4, breathing appendages. 
domen forms a long, sharp spine. The cephalo-thorax is 
broad, shaped like a horse’s foot; the feet are arranged 
about the mouth. The abdomen bears six pairs of broad 
swimming feet, except the first having upon the under 
side a set of about one hundred respiratory leaves or 
plates. The young resemble the extinct trilobites, to 
which they are allied. Some of the extinct forms, as Fig. 
109, attained a length of nine feet. 
VALUE OF CRUSTACEANS.—They are all valuable scavengers. The 
crab, lobster, and shrimp fisheries give employment to thousands of 
persons. The cocoanut-husks that the great Birgos tears up to line its 
nest are used by the Malays in basket and mat making. Concretions 
