eae 
SMALL SPECIES 379 
pereeon are prolonged into long curved spiny processes. ‘l'o 
save research into classical authorities for the origin of the 
name of this genus, it may be mentioned that it was taken 
from the title-rdle of a popular comic operetta by Gilbert 
and Sullivan. 
Jeera, Leach, 1814, is distinguished from mary of the 
preceding genera by its shorter second antennz, shorter 
limbs, and especially by the uropods, which are very short 
and have two diminutive branches. ‘There are two British 
species, Jera allifrons, Leach, and Jera 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. Jera Guernet, Dollfus, is an inland river 
species of the Azores. 
Jeeropsis, Koehler, 1885, is distinguished from Jara by 
its very small pairs of antenue, its narrow pereon with 
the segments laterally set apart, and other particulars. 
The type, Jeropsis brevicornis, was taken at Sark. All the 
species are minute. Jwropsis marionis, Beddard, is founded 
on a specimen less than a sixth of an inch long. The 
length of Jeropsis neo-zelanica, Chilton, is about a tenth 
of an inch. 
Jamna, Bovallius, 1886, was instituted to receive Jeera 
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 antennz 
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 branches 
narrow. Haswell describes Stenetrium armatum and 
Stenetrium imnerme from Australia, Chilton, Stenetrium 
fractum from New Zealand, Beddard, Stenetriwm Haswelli, 
from South America. 
Munna, Kroyer, 1839, has the head large, the pleon 
fused into a single segment ; the eyes extremely prominent, 
the second antennz very long, with their bases below the 
short first pair. The limbs of the perzon of the first pair 
