30i A HISTORY OF RECENT CRUSTACEA 



second pair of per^eopods spinose, with the third joint nofc 

 defined ; the fourth pair in the female without any rudi- 

 ment of the exopods. Vaunthomijsonia cristata, Spence 

 Bate, is British. The only other species, Vaunthompsonia 

 meridionalis, Sars, is from Kerguelen. Vaunthompsonia 

 anomala^ Sars, is supposed by its author to represent in 

 all probability another distinct genus. 



Leptocuma^ Sars, 1873, has the body elongate and 

 much compressed, the eye indistinct, the third joint in the 

 second pera3opods defined, and the fourth per^eopods in 

 the female with rudimentary exopods. The siugle species 

 is Leptociima KinOergii, Sars, taken off the mouth of the 

 Rio de la Plata. 



Heterocuma, Miers, 1879, has the eye well developed, 

 and the second joiot of the third maxillipeds produced. 

 It has the single species Heterocuma Sarsii., Miers, with a 

 variety, cjramdata. 



Fam ily 3 . — Leucon idee. 



The form is generally slender with elongate pleon. The 

 eye is wanting*. The first antennae have one of the flagella 

 small, one-jointed. The anterior branch of the mandibles 

 is without the usual series of spines, the molar tubercle 

 is massive. The ' palp ' of the first maxillaa has a single 

 terminal seta. The epipod of the first maxillipeds has few, 

 finger-like branchial sacs. The third maxillipeds are 

 rather short, with some strong set^e on the outer margin. 

 The first three pairs of perasopods in the female and the 

 first four in the male have well-developed swimming- 

 branches. The second pair of per^eopods are only six- 

 jointed. There are only two pairs of pleopods in the male. 

 The inner branch of the uropods is two-jointed, spinose, 

 the outer being setose. The telson is wanting. 



The family contains three genera. 



Leucon^ Kroyer, 1846, has the body slender, the pseudo- 

 rostral projection distinctly prominent, and the 

 first antenna3 not geniculate. There are eleven 

 species known, of which the oldest Leucon nastca, 

 Kroyer, has been recorded from British waters. 



