492 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 8S 



ARGULUS MEGALOPS Smith 



FiGUEE 31 



Argulus megalops Smith, 1873, p. 575. — Wilson, 1902, p. 706, pis. 11, 26; 1932, 



p. 16, fig. 5. 

 Argulus varians Bebe, 1936, p. 579, pi. 1, figs. 11-16. 



Carapace elliptical, male more rounded, in most instances reaching 

 third appendages on both sexes, but on Florida specimens it may 

 extend onto abdomen ; cephalic area prominent, eyes large, well sepa- 

 rated; posterior sinus broad, alae rounded; last segment of thorax 

 broadened laterally, almost as wide as abdomen. Abdomen of female 

 subtriangular, sinus shallow ; male elliptical, connected to thorax by a 

 narrow neck, almost as long as female, sinus shallower, anal furcae 

 basal. The respiratory areas well separated, anterior one compara- 

 tively large, posterior with lobed margin (fig. 31, h). Female up to 

 7 mm. in length and male the same size. U.S.N.M. No. 60462, labeled 

 A. megalops var. spinosus, is apparently not different from the reg- 

 ular species, except that there is less color and the spines on the 

 ventral surface of the carapace show up better. Both have a very 

 spinose under surface. Specimens labeled A. varians in the Bass 

 Biological Laboratory differ only in a considerable variation of the 

 size of the carapace. Other characters are identical. 



Antennae slender, spines and hooks slender, lateral hook short, 

 curved back on itself sharply, anterior knob long, with slight hook; 

 spine on ventral surface of hook long and curved; slender spines 

 present at base of first and second antennae and at midline; second 

 antennae reaching almost to edge of carapace, many setae at each 

 joint and on tip. 



Suction cups small, separated somewhat, rim supported by ribs 

 made up of an elongate rod and four to nine apparently imbricate 

 plates (fig. 31, a). Second maxillae with broad basal plate having 

 three slender widely spaced teeth; two postmaxillary pairs also 

 slender. 



Swimming appendages without flagella. Female with slender 

 boot-shaped lobe with a broad heel and slender toe on posterior sur- 

 face of fourth appendage. This varies somewhat in size. Tactile 

 papillae slender and small. 



Male third appendage with a fingerlike projection on the dorsal 

 anterior distal edge of the coxa pointing anterolaterally, and on the 

 posterior surface of the same segment is a large rounded lobe con- 



