KEVIEW OF GENUS ARGULUS MEEHEAN 507 



laterally. The exopods are distinguished from those of other species 

 by being dark in contrast to the endopods. 



ARGULUS MACULOSUS Wilson 



FiGTJEE 40 



Argulus maculosus Wilson, 1902, p. 715, pi. 19, pi. 26, fig. 82; 1907, p. 416, 

 pi. 31, figs. 15-22 ; 1914, p. 354. • 



Carapace about as wide as long; sinuses sharp but not deep, alae 

 reaching or covering third appendages; abdomen on male almost 

 rectangular, but subtriangular on female; anal sinus fairly deep, 

 with sides flaring somewhat. Tactile papillae very prominent. The 

 respiratory areas consist of a small one in a notch on the mesial 

 side of the larger (fig. 40, a). 



Antennae with three spines along the midline, the posterior one 

 broader and longer. There is an anterior hook on first antennae 

 as compared with a knob on americanus, but the knob on proximal 

 edge of basal segment of first antennae is not so prominent. There 

 is a slight papilla above spine at base of second antennae. Suction 

 cups supported by ribs composed of three to eight rods, as compared 

 with two in americcmus (fig. 40, h). Basal plate of second maxil- 

 lae with long teeth, plate narrow, postmaxillary spines long. 



Swimming appendages with flagella; fourth appendage of female 

 with boot-shaped lobe with broad heel, extending beyond the ab- 

 domen; third appendages with slight posterior ridge, precoxae long, 

 especially on male. Second thoracic appendages of male with the 

 usual posterior lobe but extended laterally (fig. 40, c). It does not 

 have the papilla under it that is found in americanus. Third ap- 

 pendage with anterior flap on coxa extending over basis; basis ex- 

 panded posteriorly with socket. The peg is very broad at the base 

 extending over the whole anterior surface of the basis; the tip is 

 unusually large and turned somewhat anteriorly. The posterior lobe 

 of the coxa is extended laterally around the basis. 



There is considerable similarity between americanus and maculo- 

 sus and between the females of versicolor and the other two. A. ma- 

 ddosus can be separated from americanus by the following points 

 of difference: On the former the rounded anterior respiratory area 

 is small and mesial, but on the latter it is large and at the antero- 

 mesial corner of the larger, more posterior one. The former has an 

 anterior hook on the first antennae, while on the latter there is a 

 knob. On maculosus the third spines at the midline near the an- 

 tennae are longer and larger, and the mesial knob at the base of 

 the first antennae is not very prominent. There are four to six rods 

 in the sucking disks of maculosus and only two in americanus. The 



