OXYSTOMATA RESPIRATORY MECHANISMS 



187 



the chelipedes properly in position. The inhalant openings are situ- 

 ated just in front of the chelipedes. It is a most remarkable fact 

 that among the Cjclometopa, Lupa Jiastata(Fig. 1 3 l)has an exactly 

 similar arrangement. Apparently we have here another instance 



Pig. 129. — Dorsal view of Matuta hanksii, x 1. (From can original drawing 

 prepared for Professor Weldon.) 



of convergence, similar to that of Corystes and AJhunea, but the 

 case is complicated by the fact that some of the Oxystomata, and 

 among them Ilatuta, show a certain amount of relationship to 

 the Cyclometopous Portunids, so that it is just conceivable that 

 the resemblances in the respiratory arrangement are due to a 

 common descent and not to convergence. 



In the Leucosiidae, of which the Mediterranean Ilia nucleus 

 (Fig. 130) is an example, the inhalant aperture is situated between 

 the orbits, and leads into gutters excavated in the " pterygo- 

 stomial plates " flanking the mouth, which are furnished with 

 filtering hairs and are converted into closed canals by expansions 

 of the exopodites of the third maxillipedes. Thus these Crabs 

 possess a filtering apparatus independent of the chelipedes and of 

 the margin of the carapace. 



Fam. 1. Calappidae. — Cephalothorax rounded and crab-like. 

 The abdomen is hidden under the thorax, the antennae are 

 small, and the legs normal in position. The afferent openings 

 to the gill-chambers lie in front of the chelipedes. Male open- 

 ings on coxae of last pair of legs. Calaiiim (Fig. 128) circum- 



