AMERICAN PARASITIC ARG ULID.^- WILSON. 713 



The types of this species are in the museum of the State University 

 at Columbus, Ohio. 



{lepidosteus=gQnQr\c name of its host.) 



ARGULUS STIZOSTETHII Kellicott. 

 Plate XVII. 

 Argxdus stlzodeilmrKm.\.icoTr, Amer. Jour. Micros., V, 1880, p. 53. 

 Carapace elliptical, much longer than wide; posterior siruis one-third 

 the length of the carapace, twice as long as wide. 



Abdomen long and narrow with parallel sides, one-half the length 

 of the rest of the body, twice as long as wide; anal sinus cut ])eyond 

 the center, narrow and slit-like toward the base, but flaring widely 

 toward the tip; lobes acute; papilhe basal. 



Cephalic area projecting considerably anteriorly. Sucking disks 

 large, moi-e than one-quarter the width of the carapace; posterior 

 maxillipeds large and stout, their ventral surface thickly covered with 

 sette; basal plate large, triangular, and armed with stout sharp teeth. 

 Antenna? large and well armed, median spine at the base of the second 

 pair particularly stout. Swinuuing legs reaching far beyond the edge 

 of the carapace; lobes on the basal joints of the posterior legs small 

 and conical. Flagella present; small papilla? at the opening of the 

 oviduct. Chitin rings in the lateral lobes of the carapace fused into 

 one whose anterior end is about the normal size, while the posterior 

 part is much narrowed, giving the whole ring a club-shaped appearance.^ 

 In the male the distal joint of the basipod of the second pair of 

 swimming legs carries upon its ventral surface a large fleshy plate or 

 lamella which projects backward, outward, and inward beyond the 

 respective margins of the joint, and whose surface is covered with 

 small sharp spines. There are also the usual capsule and peg on the 

 third and fourth legs, respectively, while the lobe on the basal joint of 

 the posterior legs is smaller than in the female. The carapace is 

 shorter than in the female, barely covering the second swimming legs; 

 the abdomen is relatively much longer and narrower-, and in Kellicott's 

 figure it is represented as fringed with setii?. 



Length, QS) mm. ; length of carapace, 4.2 mm. ; breadth of carapace, 

 8.1 mm.; length of a])domen, 2 mm.; breadth, 1.1 mm. 



These are the measurements of the specimens at my disposal, l)ut 

 Kellicott says that the females reach a size of 0.55 inch, which would 

 ])e more than twice the above measurements. The males are about 

 three-quarters as large 



Color. — Males and immature females are nearly colorless, with the 

 sexual organs brown; mature females have the carapace, legs, and 

 abdomen pale pea-green. The upper side of the thorax is darkened 

 by the usual pigment spots, while the under side is white from the 

 ripening eggs. "There is a light line along the dor^'um." 



