360 A HISTOEY 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. 



Si)hcerdma, Latreille (in Bosc), 1802, has the body 

 usually contractile into a sphere, as implied by the name ; 

 the teison is without any apical incision. Neither pair of 

 antenna is elongate ; the mandibles have a dentate cutting- 

 edge and strong molar ; the first maxilla have denticulate 

 spines on the outer plate ; the maxillipeds have the ' palp ' 

 strongly ciliated. The limbs of the pera^on 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 laminar, 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, Spliceroma serratum 

 (Fabricius) is occasionally found on the shore in large 



