Introduction to Animal Morphology. 361 



the freshwater shrimp, has a large antennule and a mandi- 

 bular palp. Lysianassa has no prehensile feet. Chelura 

 ttrcbrans bores into submerged timbers, 2. Hyperidae 

 marine, often of extraordinary shapes ; head large, thick ; 

 antennae often rudimental ; second maxilla three-jointed ; all 

 the limbs are prehensile, and the uropoda form a swimming 

 tail ; the body is not bent as in Gammaridae, so they cannot 

 leap. Phronima has only one pair of antennae. 



Order 4. Isopoda (Latreille} integument membranous, 

 rarely calcified ; segments nearly homonomous, dorsally com- 

 pressed ; the two hinder thoracic limbs and the five abdominal 

 legs equal, ambulatory ; the post-abdominal feet lamellose ; 

 maxillipede forming a lower lip ; the intra-ovular Nauplius has 

 two trefoil-like side processes, representing the carapace, 

 spines and gills of Zoea, but on emission from the egg the larva 

 only differs from the adult by wanting the fifth abdominal 

 pair of legs ; the embryo in the egg is ventrally turned, as in 

 Schizopods, not dorsally, as in Amphipods or most Decapods ; 

 the first thoracic segment is free from the head, except in 

 Praniza, where the three thoracic segments and head unite ; 

 the gills are attached to the pleiopoda, each of which has ex- 

 ternal to it an epipodial membrane, which is delicate and 

 n >piratory in the aquatic, thick, tile-like protective in the 

 terrestrial forms ; the antennae are four; the eyes often close 



'ther ; the eggs are sometimes carried in brood-pouches 

 attached to the legs ; there is a mandibular, but no maxillary 

 palp. 



The following families are included : i. Pranizidae with 



two larp^e pair of antennce ; head and thorax fused ; last 



pleiopod and telson forming a tail ; ambulatory limbs five 



> ic rudimc-ntnl ; the young and the female Praniza 



are suctorial and parasitic; the adult male is '.has 



the nan, . 2. Ilopyrido: male 



1 ; female l>n .:i^\ nnnetriral, with no 



:ulibular ; '. ;i rudimental mouth ; parasitic on other 



attarhrd to the females, us in 

 Siphonostomata. I!j.yrus has in the female lainell< 



; I.iiiuj -.:Mtic on 



.site Pcltoga- ,anurki-like, with 



