488 CRUSTACEA MALACOSTRACA. 



Fam. 1. Asellidae. Body flattened, antennae with long flagella. All, 

 or all but the first, abdominal segments fused and covered by a caudal 

 shield. The two anterior pairs of abdominal feet small, the three next 

 large and respiratory, the sixth styliform or lobed, and projecting pos- 

 teriorly. Marine and fresh water. Pleurogonium Sars ; Leptaspidia 

 Sp. Bate ; Jaera Leach ; Janira Leach ; Asellus Geoffr. (Fig. 295) ; 

 Munna Kro'y. ; Ischnosoma Sars: Paramunna Sars ; Macrostylis Sars. 



Fam. 2. Munnopsidae. Eyes absent. Body elongated, often wide in 

 the second in the fifth thoracic segments which bear elongated legs, and 

 suddenly narrowed in the three posterior which bear lamellar swimming 

 feet ; abdomen unsegmented. Deep-water forms generally in high (N. 

 and S.) latitudes. Desmosoma Sars ; Munnopsis M. Sars ; Ilyarachna 

 Sars ; Eurycope Sars ; Acanthocope Beddard. 



Tribe 3. PHREATOICIDEA. 



Fam. 1. Phreatoicidae. Contains the two spp. of Phreatoicus described 

 by Chilton,* P. typicus from a well in N. Zealand, and P. australis from 

 5,700 ft. on Mt. Kosciusko in the Australian Alps, and from Mt. Wellington 

 in Tasmania. In the laterally compressed body, the disposition of the 

 thoracic legs in two sets, the anterior curved backwards and the posterior 

 forward, and other features, they present a remarkable resemblance to 

 Amphipods. In the characters of mouth parts and pleopods they are 

 however distinctly isopodan. 



Tribe 4. VALVIFERA. 



Elongated Isopods with palpless mandibles and abdominal terga fused 

 to a caudal plate. The five anterior abdominal appendages are respira- 

 tory, covered by the valvular uropods, which are lateral. 



Fam. 1. Areturidae. 2nd antennae very long, the 2nd-5th thoracic 

 legs setose, with minute terminal claws. Arcturus Latr. The 5th thoracic 

 segment not much larger than the others. Astacilla Cordiner (Leacia 

 Johnst.) 5th thoracic segment much elongated. 



Fam. 2. Idoteidae. 2nd antennae not very long, strong claws on 

 the anterior thoracic legs. Chaetilia Dana ; Edotia Guer. ; Erichsonia 

 Dana ; Arcturides Studer ; Cleantis Dana ; Idotea Fabr. ; Glyptonotus 

 Eights ; O. antarcticus Eights, attains a length of 3J inches and a 

 breadth of 1 f inches. 



Tribe 5. FLABELLIFERA. 



Uropods lateral, forming with the telson a terminal fin. The other 

 abdominal limbs generally natatory. 



Fam. 1. Anthuridae. Body linear, cylindrical, with short nearly 

 equal antennae, and in some cases with piercing mouth-parts. One pair 

 of maxillae absent. The anterior five pairs of abdominal feet respiratory, 

 covered by a horny operculum the exopodites of first pair ; sixth pair 

 enclosing the terminal abdominal segment between them. Anthura 

 Leach, with paired otocysts in the telson ; Cyathura, Anthelura and 

 Hyosura Norm, and Stebbing ; Eisothistos Haswell, E. vermiformis Haswell, 

 in the tubes of the Serpulid Vermilia. Haliophasma Haswell ; Ptilan- 

 thura Harger ; Paranthura Sp. Bate : Calathura Norm, and Stebbing ; 

 Cruregens Chilton. 



Fam. 2. Sphaeromidae. Body oval, highly arched, rolling more or 



* C. Chilton, Records of the Australian Museum, vol. i. (1891), p. 149. 



