360 A HISTORY OF RECENT CRUSTACEA 
branch. The uropods are affixed near the base of the 
terminal segments, and have not more than one branch that 
is movably articulated. 
The family is at present in a state of considerable 
confusion, Genera and species have been established on 
characters which, it has since been ascertained, are, at 
least in some instances, only marks of age or sex. In 
recent years various suggestions have been made for can- 
celling several of the genera so established, but without 
any effective investigation to determine whether there may 
not be valid distinctions to take the place of those which 
have proved inappropriate. In the very erudite and com- 
prehensive work on the Crustacea by Gerstaecker, now in 
course of publication in Germany, the reduction of genera 
has been carried far beyond what will, I think, be found 
eventually tenable. In several of the genera the character 
that has attracted earnest attention has been some dorsal 
spine developed, now on one, now on another part of the 
animal. As a rule, it now appears that these outgrowths 
belong to the male, and not to the female, but the attempt 
to refuse them all generic value on this account is not 
likely to be successful. 
Spheroma, Latreille (in Bosc), 1802, has the body 
usually contractile into a sphere, as implied by the name ; 
the telson is without any apical incision. Neither pair of 
antenne is elongate; the mandibles have a dentate cutting- 
edge and strong molar; the first maxille have denticulate 
spines on the outer plate ; the maxillipeds have the ‘ palp’ 
strongly cilated. The limbs of the perzon are all ambu- 
latory, not powerful, but with short and thick fingers. 
The upper or outer branch of the fourth and fifth pleopods 
is thin and Jaminar, acting as an operculum to the pleated 
branchial inner branch. The outer branch in these and 
sometimes also in the third pair is unequally divided by 
a suture. ‘The free outer branch of the uropods is sub- 
equal to the prolongation of the peduncle which represents 
the inner branch. The species are numerous, but not all well 
ascertained. Of the British species, Sphaeroma serratum 
(Fabricius) is occasionally found on the shore in large 
f 
