364 



ART1CULATA : CRUSTACEA. 



a rudimentary abdomen ; authors describe these forms 

 under the name of L.EMODIPODS (from the Greek laimos^ 

 threat, di, two, and jr;<ms', foot). 



SUB-SECTION IV. 



FIG. 494. 



THE ORDER OF ENTOMOSTRACA OR ENTOMOSTRACANS. 



THE Entomostraca are crustaceans which are defective 

 both in segments and feet, as compared with the two pre- 

 ceding orders, and rank ]ower. The name is from the 



o . 



Gr. entomos, an insect, and ostrakon, a shell. 



Normally they have six, or five, cephalic rings, and eight 

 or nine posterior rings belonging to the foot series. More 

 or less of these, however, are usually wanting. The abdo- 

 men is also without appendages. 



The MEROSTOMATA (from the Greek meros, thigh, and 



stoma, mouth), are entornos- 

 tracans which are represent- 

 ed by only one living genus 

 (Limidus the Horse-shoe 

 Crab). The group is often 

 called Limuloidea, and also 

 Xiphosura or sword-tailed. 



The Horse-shoe Crab at- 

 tains the length of one or 

 two feet, and is especially 

 remarkable from the fact 

 that it uses the same organs 

 both in locomotion and in 

 eating the thighs of the 



Horse-shoe Crab in the egg just before 

 hatching magnified. 



