new arid rare Crustacea from Scotland. 459 



Canthocamptun palustris, var. elonqatiis^ var. n. 

 (PI. XVI. figs. 7-17.) 



Description of the Variety. — Female. Leiiixtli *7 millim. 

 (^ of ail inch). Body elongate and slender. Antennules 

 eight-jointed; the second, t'ouith, and last j(jints are subequal 

 and longer than the other joints, but the seventh joint is 

 considerably shorter than any of the others ; the formula 

 shows the proportional lengths of the joints very nearly — 



Proportional lengths of the joints. . 9 . 1 2 . 7 . 1 1 . 7 . 8 . .5 . 10 

 Number of the joints 1 2 3 4 6 6 7 8"" 



Antennae moderately stout, three-jointed ; the first joint ia 

 short, the second and third are longer and nearly equal in 

 length; secondary branch small, one-jointed (fig. 9). Man- 

 dibles slender and provided with a small two-jointed palp 

 (fig. 10). Posterior foot-jaws moderately stout ; a small 

 seta springs from the inner distal angle of the first joint, and 

 another from tiie margin of the second joint near the distal 

 end ; terminal claw about equal in length to the second joint 

 (fig. 11). Both branches of the first pair of swimming-feet 

 are short and of nearly equal length, and are both three- 

 jointed ; the inner, which is slightly the longer branch, has 

 the second and third joints short and subequal, their combined 

 length being only a little more than two thirds of the length 

 of the first joint, which is also considerably stouter ; the joints 

 of the outer branch are moderately stout and gradually increase 

 in length from the basal joint (fig. 12). The second, third, 

 and fourth pairs are more elongate than the first, and the 

 inner branches are all three-jointed and considerably shorter 

 than the outer branches ; the first joint of the inner branches 

 is also much shorter than the second and third joints (fig. 13). 

 Fifth pair broadly foliaceous ; the produced inner portion of 

 the basal joint is shorter than the secondary joint and broadly 

 rounded at the end, where it carries five slender setre, having 

 a somewhat ])ectinate arrangement ; the two outermost setas 

 are much longer than the others and j)lumose ; the secondary 

 joint is subrotundate, but somewliat longer than broad, and 

 furnished with five long slender hairs (fig. 14). Caudal 

 stylets very short (fig. 17). The abdomen is only sparingly 

 hirsute, and the ovisac is large. 



Male. The male resembles the female very closely except 

 in the antennules and filth pair of feet; the antennules are 

 elongate, nine-jointed, and strongly hinged. In the fitth pair 

 of thoracic feet the inner portion of the basal joint is scarcely 

 produced and broadly rounded, and bears three terminal and 



32* 



