12 CRUSTACEA OF ALABAMA. 



Genus Osphranticum. Forbes. 



Cephalothorax six-jointed, distal segments evident ; abdomen, in the male, five- 

 jointed, in- the female four-jointed ; antennae twenty-four jointed, the right geniculated as 

 in Centropages ; first pair of feet with the rami both three-jointed, like the following ; 

 feet of the fifth pair, in the female, like the preceding, but with a spine of the joint pre- 

 ceding the terminal one enlarged and divaricated somewhat as in Centropages ; in the 

 male, the right with a two-jointed outer ramus, the terminal joint of which is spined and 

 bears near its base a blunt expansion of its inner margin ; outer ramus of left foot three- 

 jointed, armed with unequal spines ; inner branches smaller, similar, three-jointed ; the 

 terminal joint bearing curved spines ; ovary and testes as in Diaptomus, with which the 

 mouth parts agree in the main ; eyes median, confluent. 



Osphranticum labronectum, Forbes. 



Potamoichtior fucosus, herrick, Cyclopida; of Minnesota, etc., p. 224. . 



Rather slender, and in size, as well as general appearance, resembling the smaller 

 forms of Diaptomus ; antennae rather stout, reaching but little beyond the feet, append- 

 aged as in Diaptomus, in the male strongly geniculated, but somewhat variously so ; the 

 six joints preceding the terminal four are thickened ; those preceding the joint or hinge 

 are arcuate on the distal margins ; the secondary antennae are about as in Diaptomus ; 

 mandibular palp two-branched, the outer three-jointed, the inner two-jointed ; the term- 

 inal joint of the shorter branch bearing seven setae, of the other, four, the proximal joint 

 of the other with three stout spines ; the maxillae nearly like Diaptomus ; the processes 

 have respectively the following numbers of setae : the basal plate eight, the small pro- 

 cesses at base of posterior branchial appendage one, the appendage itself twelve, termi- 

 nal portion three groups, first containing nine, the second three, and the third four or 

 five, the upper of the anterior processes two, and the lower three ; fifth feet nearly like 

 the others in size ; the right in the male having the outer branch but two-jointed by the 

 coalescence of the two outer to form an arcuate and deformed appendage, armed at the 

 end with three stout equal spines ; corresponding branch of left foot three-jointed ; the 

 terminal joint bearing three unequal spines, each of the preceding joints only one ; inner 

 branches similar, three-jointed ; terminal joint being short and armed with three short 

 lanceolate setae and three longer ones, two of which are curved so as to be slightly pre- 

 hensile ; fifth foot of female with both rami three-jointed ; inner ramus much smaller ; 

 penultimate segment of the outer ramus extending into a large lanceolate process ; ova- 

 sac long-ellipsoidal or spherical, reaching nearly to the end of the caudal setae. Length, 

 .09 in., Cephalothorax, .05 in. 



In Alabama this species is very abundant and seems usually to delight in flowing 

 water rather than stagnant or quiet pools. The genus finds no homologue apparently 



