366 BUIyLETIN OP THE BUREAU OF FISHERIES. 



Slew, Fairport, August 14, 1914, catalogue no. 47742, U. S. National Museum; three copepodid larvae 

 from gill filaments of sauger in Lake Pepin, Mississippi River, August 28, 1914, catalogue no. 47743, 

 U. S. National Museum. One or two copepodid larvae were also obtained from the gills of the bullhead, 

 Ameiurus melas, in " Simfish Lake," August 20, 1914; these were preserved and used for sectioning. 



Specific characters of female. — Body club-shaped, enlarged two or three diameters posteriorly; horns 

 varying in number, size, and arrangement; usually they are four in number, short and very wide and 

 strongly flattened dorso-ventrally, so that they become thin laminae; the foiu' are arranged in pairs, 

 attached to the sides of the thorax, behind the head, the first pair just in front of the first swimming 

 legs, the posterior pair just in front of the second legs; they are all about the same size, nearly as ^vide 

 as long, and each is attached separately to the thorax and extends out nearly at right angles to the long 

 axis of the body. Sometimes the two anterior horns are much larger than the posterior ones (fig. 90) 

 and are tiu'ned forward like a large horseshoe, whose sides are parallel to the body axis; sometimes the 

 two posterior horns are more or less fused into a single one, much smaller than the lateral anterior ones. 

 Instead of being buried in the flesh these horns are often applied to the surface of the scales (fig. 92), 

 with whose substance they apparently fuse quite solidly, so as to furnish a secure attachment. 



The body is segmented and the diameter posteriorly is three times that anteriorly ; at the posterior 

 end there is a small lateral tubercle on either side, ventral to the egg string, and a much larger median 

 dorsal tubercle, the abdomen, which reaches far behind the lateral ones; the anal papillae are compara- 

 tively large and jointed, and each carries three or four small setae arouijd the base in addition to the 

 large terminal one. 



The egg strings are narrow and elongate, less than a third the length and width of the body. 



Head elliptical, a little longer than wide, without an anterior rostrum; first antennae three-jointed, 

 the two basal joints considerably longer and wider than the terminal one, and all of them heavily armed 

 with setae; second antennae two- jointed, the terminal joint half as long again as the basal and ending in 

 a single large claw and a tuft of setae, the basal joint unarmed. Mandible a single slender curved claw 

 motmted on a stout hemispherical base inside the lips; first maxilla a very much stouter claw, curved 

 abruptly near the base and bluntly rounded at the tip; second maxilla armed with the usual two stout 

 claws, also abruptly ciu-ved, but nearer the tip, which is much sharper than in the first maxilla. 



Maxilliped comparatively large and stout, tipped with five strong curved claw^, with a large blunt 

 knob at their base and a medium-sized papilla on the inner margin, tipped with a single seta. 



Color a dark creamy white. 



Body length (excluding horns and egg strings), 6 mm.; greatest diameter, i mm. Length of egg 

 strings, 3 mm.; diameter of same, 0.36 mm. 



(variabilis, variable, alluding to the size, number, and position of the cephalic horns.) 



Remarks. — This species is chiefly characterized by the four flattened horns, which are entirely 

 separated to their base and which are often attached to the surface of a scale instead of being buried in 

 the flesh. The antennae are also quite different from those of other species. 



The discovery of the copepodid larvae upon the gills of the sauger, the catfish, and the short-nosed 

 gar serves to associate this species, and presumably the others also, with gill glochidia. These larvae 

 are very similar to an adult ergasilid but are smaller and of course without egg strings. They are very 

 lively and loosen their hold (which is made by means of the curved claws on the second antennae) on 

 the gill filament at the slightest provocation and dart around over the gills rapidly, taking a new hold 

 somewhere else. For this reason they would probably offer more hindrance to the attachment of the 

 mussel glochidia than the sluggish ergasilids. At the same time the hindrance would be only tempo- 

 rary, since these are larvae whose transformation only requires a brief period for its accomplishment, 

 after which they leave the gills and fasten themselves elsewhere upon tlie body of a new host. 



Lemseocera tenuis, new species. (PI. Lxxin, fig. 102-107.) 



Host and record of specimens. — A single female was taken from the side of the body of a sheepshead, 

 Aplodinotus grunniens, at Fairport, July 16, 1914; it becomes the type of the new species and has been 

 given catalogue no. 47737, U. S. National Museum. 



Specific characters of female. — Body long and slender with very little posterior enlargement; a single 

 horn on either side of the head attached farther back than in other species, extending out at right angles 

 to the body axis, and divided into two branches, the dorsal of which is much larger and nearly four 

 times as long as the ventral; both branches are somewhat enlarged and bluntly rounded at the tip. 



