150 



The Canadian Field-Naturalist 



[Vol. XXXIV. 



F'is. 



Argulus piiieratu.><: fli'st and second 

 mtennae of male, much enlarged. 



Lateral claw of basal joint of first antenna long 

 and slender and curved into a half circle; anterior 

 claw sKcrt and weak. Second joint slender, three 

 times the length of the terminal joint, and armed at 

 the distal anterior corner with a short spine; ter- 

 minal joint tipped with two spines. Second anten- 

 na of the usual pattern, the basal joint one-half 

 wider than the succeeding joints and tipped with a 

 long spine; second joint with two spines, third and 

 fourth joints with one spine each. 



Fig. :>. Argulus pipei'atus; supporting rods in 

 sucliing disks: much enlarged. 



Sucking disks cf second maxillae far forward 

 and well separated, each about IS'/J of the width 

 cf the carapace; the supporting rods .slender and 

 far apart, each made up of four cylindrical joints 

 which diminish regularly in size from the base out- 

 wardly, and which do not quite reach the margin. 

 The latter has a fringe of flattened fleshy setae, at- 

 tached side by side in a single row. 



Fig. 4. Argulus idperatus; maxilliju'd of male; 

 Miuch cnlargi-d. 



The maxillipeds are rather short but stout; the 



triangular plate on their base is wide posteriorly 



and much narrowed anteriorly, but extends to the 



anterior margin of the appendage; the teeth are 



long and wide and bluntly rounded. Inside of the 



base of the appendage, on the ventral surface of 



the head, is an accessory tooth of the same pattern 



as those on the plate itself. 



The rami of the swimming legs reach consider- 

 ably beyond the margin of the carapace. The 

 lobes en the basal joints of the fourth legs are 

 small and not very prominent. 



Color a light cartilage gray, the dorsal surface 

 covered with small black dots, as though it had 

 been sprinkled with pepper. These dots are not 

 evenly distributed but are massed as shown in the 

 figure. 



Total length 5 mm. Caiapace 4 mm. long, 3.25 

 mm. wide. Abdomen I mm. long, 0.90 mm. wide. 



Fig. .''i. 1 )ors£l view of Argulus iiipei-atus, male. 

 Tile line rejiresents a length of 1 mm. 



Specific characters of- male. Carapace relative- 

 ly the same size and shape as in the female ; abdo- 

 men longer, cne-third the length of the carapace, 

 the longitudinal and transverse diameters in the 

 proportion of 15 to 11. Anal sinus not as deep, 

 only 14^7 of the length of the abdomen and never 

 closed by the approximation of the posterior lobes. 



^A ^ 



Fig. fi. 



.\rgulu 

 cnlai-i 



piperatu.'- 



I'd. 



third 1( 



>f male, much 



Of the accessory sexual characters the peg on 

 the anterior margin of the basal joint of the fourth 

 legs is a broad cone, inclined strongly outwards and 

 bluntly rounded at the tip, with a tiny spine on its 



