342 PROCEEDINOS OF THE NATIONAL MUSEUM. vol.39. 



Exopods of the fourth swimmmg legs two-jointed, all the other 

 rami three-jointed; fifth legs rudimentary, each consisting of a small 

 papilla tipped with two spines, the outer of which is longer than the 

 inner. The arrangement of the spines and setse on the first four 

 pairs of legs is as follows : First exopod, I-O ; 0-1 ; II-4 : endopod, 

 0-1; 0-2; 1-3: second exopod, I-O; 0-1; 1-4: endopod, 0-1; 0-2; 

 II-4: third exopod, I-O; 0-1; 1-5: endopod, 0-1; 0-2; 1-4: fourth 

 exopod, 0-0; 1-5: endopod, 0-1; 0-2; 1-3. 



Color of body in general a pale transparent horn or cartilage tint; 

 ovary a cream yellow; ventral surface covered with a network of 

 brilliant violet purple, in spots and delicate threads; dorsal surface 

 with spots of pale cinnamon brown, irregularly distributed, with very 

 few lines ; digestive tube a rich rust color. As the center of the body 

 is transparent this pigment of the digestive tube shows plainly in 

 both dorsal and ventral views as a broad longitudinal line, bordered 

 on either side by the creamy yellow of the ovaries, with an outside 

 margin of the cinnamon brown spots. Eyes a dark reddish brown, 

 almost black; a large space behind the eyes and in front of the diges- 

 tive tube clear and transparent. 



This assemblage of tints makes the present species the most highly- 

 colored of its genus and has suggested its specific name. 



Total length, 1.56 mm. Length of cephalothorax, 0.8 mm; width 

 of same, 0.46 mm. Length of free thorax, 0.4 mm. Length of geni- 

 tal segment and abdomen, 0.32 mm. Length of egg-strings, 0.95 

 mm. 



(versicolor, variegated, showing many colors.) 



This species was fairly common on the two kinds of catfish found 

 at Lake Maxinkuckee, Indiana, Ameiurus nehulosus, the common 

 bullhead and A. natalis, the yellow cat. 



The latter was more often infested with the parasite than the for- 

 mer. This species was never found upon any other fish although 

 many hundreds of them were searched for it. Nor was Ergasilus 

 centrarchidarum, which was so common on the other fish, ever found 

 upon either of these catfish. 



In this respect the present species appears to have a well-defined 

 habitat. The National Museum collection includes five lots of this 

 parasite distributed as follows : No. 38652 from the gills of Ameiurus 

 natalis at Lake Maxinkuckee, contains specimens which are made the 

 types of the new species. Two other lots from the same host and 

 locality are numbered, respectively, 38650 and 38651. No. 38649 

 includes half a dozen specimens from the gills of A. natalis in the 

 Mississippi River at Alton, Illinois. No. 38648 contains eight 

 females from the gills of the channel cat, Ictalurus pundaius, captured 

 in the Mississippi River at Clayton, Iowa, 



