COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 361 



The upper lip is diamond shaped, considerably longer than wide, the anterior end well rounded, 

 the posterior end pointed, and reaching some distance behind the masticatory processes of the second 

 antennas. 



The balancers at the posterior end of the body are straight instead of curved and stand at an angle 

 of about 45 degrees with the body axis. 



Remarks. — The large numbers (500 or more) of specimens found upon a single fish are worthy of 

 notice; in some instances it does not seem as if any more could be crowded upon the gills, three or four 

 copepods being found, one above another, upon the same filament. Like the original specimens from 

 the bluegills, they are always found on the inner side of the gill filament, between the rows of filaments 

 ontlie same arch. 



Here in the Mississippi Valley the two crappies are evidently the chief hosts of tlie species and it 

 is worthy of note that they are vegetable feeders like the bluegill. This species of ErgasUus therefore 

 may be fairly regarded as a parasite of the vegetarian Centrarchidae. 



It is also worth recording that of the many hundreds of ccsrukus examined every one was scrupu- 

 lously clean; there were no protozoa or algae upon any of the specimens. This is in marked contrast to 

 the following species from the catfishes, nearly every specimen of which is covered with these para- 

 sites. The present species is associated with the Lampsilis group of glochidia and has been found upon 

 every species of fish that serve as hosts for these glochidia except the sheepshead and the largemouth 

 black bass, on which latter fish it is replaced by E. nigritus, a new species. 



Ergasilus versicolor Wilson. 



ErgasUus versicolor Wilson, Proc. U. S. Nat. Mus., vol. 39, p. 341, pi. 45. 



Host and record of specimens. — Originally found upon two species of catfish at Lake Maxinkuckee, 

 Ind., this ergasilid proves to be even more abundant upon the catfishes of the Mississippi, and the fol- 

 lowing lots were obtained during tlie summer: Catalogue no. 43558, U. S. National Museum, from the 

 gills of the skipjack, Pomolobus chrysochlorus , taken in Lake Pepin and sent to Fairport July 23; cata- 

 logue no. 47770, U. S. National Museum, from the gills of the channel cat, Ictalurus punctatus, taken at 

 Faiqiort July 25; catalogue no. 43533, U. S. National Museum, from gills of channel cat taken at Fair- 

 port September 2, 1910; catalogue no. 43560, U. S. National Museum, from gills of the bullhead, Amei- 

 uriis nehulosus, taken in Patterson Lake July 3; catalogue no. 43509, U. S. National Museum, from 

 gills of the Fulton cat, Ictalurus anguilla, taken at Fairport May 14, 1914. 



Remarks. — All these specimens except those Included in no. 47770 were heavily infested with 

 parasitic protozoa and fresh-water algae, and some were so thoroughly covered as to be effectively con- 

 cealed. This is probably due in part to the feeding habits of their hosts, all of whom stick close to the 

 mud at tlie bottom of the river. 



The species is associated with the Quadrula group of glochidia and in all probability will be found 

 upon Leptops otivaris, the mud cat. 



Ergasilus centrarchidarum Wright. 



ErgasUus cenlrarchidar^im Wright, Proc. Canadian Institute, n. s., vol. i, p. 243, pi. i; Wilson, Proc. U. S. Nat. Mus., vol. 

 39. p. 33". Pl. 42- 



Host and record of specimens. — In addition to those found upon various hosts at Lake Maxinkuckee, 

 Ind., and recorded in the last reference given above, the following lots were obtained during the past 

 summer: Catalogue no. 43507, U. S. National Museum, from the gills of Pomoxis annularis, taken in the 

 Mississippi at Fairport, May 25, 1910; catalogue no. 43337, U. S. National Museum, from the gills of the 

 largemouth black bass, M. salmoides, taken in Crooked S Slew, Fairport, May 26, 1910; catalogue no. 

 47778, U. S. National Museum, from the gills of the white bass, Roccus chrysops , taken at Fairport, August 

 6; catalogue no. 47775, U. S. National Museum, from the gills of the sauger, S. canadense, taken at Fair- 

 port, August 14: catalogue no. 47779, U. S. National Museum, from the gills of the largemouth black 

 bass, taken in Patterson Lake, August 6; catalogue no. 47780, U. S. National Museum, from the gills 

 of the warmouth, Ckcenobrytlus gulosus, taken in Patterson Lake, August 6. A single female was also 

 obtained from the gills of the green sunfish, Apomotis cyanellus, taken at Fairport, August 10. 



Reinarks. — This species is frequently associated with cceruleus upon the same host, but the two can 

 always be separated by their position on the gill filaments; centrarchidarum is always on the outside, 

 while cceruleus is as constantly on the inside between the two rows of filaments, and no exception has 

 yet been found to this rule. 



