SMALL SPECIES 379 



peraeon are prolonged into long curved spiny processes. To 

 save researcli into classical authorities for the origin of the 

 name of this genus, it may he mentioned that it was taken 

 from the title-role of a popular comic operetta by Gilbert 

 and Sullivan. 



Jce,ra^ Leach, 1814, is distinguished from many of the 

 preceding genera by its shorter second antennae, shorter 

 limbs, and especially by the uropods, which are very short 

 and have two diminutive branches. There are two British 

 species, Jcera albifrons, Leach, and Jcera Nordmanni 

 (Rathke), both very small. The former, which is rather 

 the larger, has a very extensive northern distribution. 

 Both are often at home in runlets of fresh water travers- 

 ing sea-beaches. Jcera Guernei, Dollfus, is an inland river 

 species of the Azores. 



Jcero^ms^ Koehler, 1885, is distinguished from J(jera by 

 its very small pairs of antennae, its narrow perseon with 

 the segments laterally set apart, and other particulars. 

 The type, Jcerojjsis hrevicornis, was taken at Sark. All the 

 species are minute. Jceroj^ds marionis, Beddard, is founded 

 on a specimen less than a sixth of an inch long. The 

 length of Jceropsis oieo-zelanica, Chilton, is about a tenth 

 of an inch. 



Jamna, Bovallius, 1886, was instituted to receive Jcera 

 longicornis, Lucas, from Algeria, in which the first limbs 

 are chelate, and the uropods are two-branched, with the 

 branches longer than the peduncles. 



Stenetrium^ Haswell, 1881, has the second antenna? 

 long,. and carrying an exopod. The first limbs are chelate 

 or nearly so. The terminal joint is bifid in the following 

 pairs. The uropods are two-branched, the branchea 

 narrow. Haswell describes StenctriuTn armatum and 

 Stenetrium inerme from Australia, Chilton, Stenetrmm 

 fradum from New Zealand, Beddard, Stenetrium Haswellij 

 from South America. 



Mimna, Kroyer, 1839, has the head large, the pleon 

 fused into a single segment ; the eyes extremely prominent, 

 the second antennae very long, with their bases below the 

 short first pair. The limbs of the pereeon of the first pair 



