THE HORSESHOE CBAB. 



95 



Class II. — Podostomata {King-crab, Eurypterus, and 

 Triloiites). 



Order 1. Merostojnaia. — The only living representative 

 of this ordA- is the horseshoe or king-crab {Lhmdus Poly- 

 phemus, Fig. 122), which ranges from Oasco Bay, Maine, 

 to Florida and the West Indies. 



The body of the king-crab is very large, sometimes nearly two 



^lo. 119.— Common Shore-crab (Cancer ij-rorahts). Natural size. FromEmertoa 



feet in length; it consists of a head composed of six segments and 

 an abdomen witli nine segments, the ninth (telson) forming a long 

 spine. The head is broader than long, in shape somewhat lilve tliat 

 of Ap^is, witli a broad flat triangular fold on the under side. Above 

 are two large lunate compound ej'es, near the middle of the head, 

 but quite remote from each other, and two small compound eyes sit- 

 uated close together near the front edge of the liead. There are no 

 antenna}, and the six pairs of aiipendages are of uniform shape lilve 

 legs, not like mandibles or maxilla', and are adapted for walking: 

 the feet are provided witli shaip teeth on the basal joint for retain- 



