304 A HISTORY OF RECENT CRUSTACEA 



second pair of pereeopods spinose, with the third joint not 

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

 ment of the exopods. Vaunthompsonia 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 perseopods defined, and the fourth perteopods in 

 the female with rudimentary exopods. The single species 

 is Leptocuma Kinbergii, Sars, taken off the mouth of the 

 Rio de la Plata. 



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

 and the second joint of the third maxillipeds produced. 

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

 variety, granulata. 



Family 3. — Leuconidce. 



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 maxillae has a single 

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

 fingei'-like branchial sacs. The third maxillipeds are 

 rather short, with some strong setae on the outer margin. 

 The first three pairs of peraeopods in the female and the 

 first four in the male have well-developed swimming- 

 branches. The second pair of peraeopods 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 antennas not geniculate. There are eleven 

 species known, of which the oldest Leucon na^ca, 

 Kroyer, has been recorded from British waters. 



