346 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.39. 



Labium well defined and fairly wide, with an almost straight 

 posterior border. 



Rami of the swimming legs with three joints except the exopods 

 of the fourth pair, which have but two joints. The arrangement of 

 spines and setae is as follows : First exopod, I-O ; I-l ; 1-5: endopod, 

 0-1; 0-1; 1-5: second exopod, 0-0; 0-1; 0-6: endopod, 0-1; 0-2; 

 0-4: third exopod, 0-0; 0-1; 0-6: endopod, 0-1; 0-2; 0-5: fourth 

 exopod, 0-0; 1-5: endopod, 0-1; 0-2; 0-4. Fifth legs made up of 

 a single short joint tipped with two small setfB of equal length. 



Color yellowish brown at the extreme front of the cephalothorax 

 and along the free thorax, the abdomen, and the egg-strings, deepening 

 to a dark brown through the cephalon and first thorax segment. On 

 the ventral surface there is a line of spots and streaks of dark blue 

 pigment on either side passing through the basal joints of the swim- 

 ming legs and running forward, about the same distance apart on the 

 cephalothorax, to the bases of the second antennae. There is a large 

 spot of the same pigment on either side of the mid line and close to 

 it, at the anterior end of the genital segment, and two other similar 

 spots at the bases of the anal laminae. 



Total length, 1.15 mm. Cephalothorax, 0.73 mm. long, 0.46 mm. 

 wide. Width of second segment, 0.15 mm. Length of egg-strings, 

 1.65 mm. 



(mugilis, the generic name of its host.) 



The collection of the National Museum contains but a single lot of 

 this species, consisting of two females taken from the gills of Mugil 

 ceplialus, the common mullet, at Beaufort, North Carolina, in the 

 summer of 1901 by Prof. Edwin Linton, and numbered 38631. The 

 species is not a common one, since the examination of many fish 

 yielded but these two specimens. The large cephalothorax, dis- 

 tinctly grooved at the center and the exceptionally long and narrow 

 egg-strings will help to distinguish this from other species. 



In 1877 Carl Vogt published in the second memoire of his Re- 

 cherches Cotieres a short description of a species of Ergasilus. His 

 specimens also were taken from the gills of the common mullet, which 

 is the same in European waters as on our Atlantic coast. He 

 described nothing but the external appearance of the parasites, hav- 

 ing unfortunately mislaid the specimens upon which he intended to 

 work out the mouth-parts and other appendages. He gave the 

 species the provisional name of E. mugilis; provisional because to 

 the best of his belief the species was identical with one which Hesse 

 had obtained on Mugil cajnto, and upon which the latter author had 

 founded a new genus and species, MegabracTiinus suhoculatus. If 

 the two proved to be the same, Hesse's generic name would have the 

 precedence: if not, then Vogt's name would become valid. 



