NO. 21»4. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 37 



margin; all the horns conical and soft; neck soft, slender, and 

 cylindrical, enlarging gradually into the trunk which is also cylin- 

 drical; trunk with a pregenital prominence in front of the vulvae; 

 abdomen short and bluntly rounded, terminating in a pair of minute 

 anal laminae; egg strings elongate-conical or ovoid, eggs multi- 

 seriate. 



Two pairs of antennae, second pair uncinate; proboscis conical 

 and very short; mandibles claw-shaped and without teeth; two 

 pairs of maxillae; one pair of maxillipeds; four pairs of biramose 

 swimming legs, first pair just behind the head, others at increasing 

 distances posteriorly; a fifth pair of one-jointed stumps just in front 

 of the vulvae. 



Internal generic characters of female. — Esophagus short, nearly 

 straight, and diagonal to the body axis; anterior stomach with 

 lateral lobes and more or less convoluted; posterior stomach passing 

 insensibly into the intestine, which is straight, of the same diameter 

 throughout, and abruptly contracted into a short rectum; ovaries 

 paired, close to the dorsal surface and near the posterior end of the 

 trunk; matured oviducts with two long posterior and two shorter 

 anterior loops; eggs remaining spherical and never flattened antero- 

 posteriorly; no separate cement glands, the thickened glandular 

 walls of the posterior oviducts serving that purpose. 



No separate excretory glands, the chitinogen layer of the skin 

 apparently serving for excretion through the pore canals. 



Genus hah'dat. — This genus fastens to the outside surface of the 

 fish's body, usually in the vicinity of the fins, and bores into the 

 underlying tissues a short distance until it finds an adequate blood 

 supply without seeking any particular organ or blood vessel. 



Generic characters of the copepodid male. — The external generic 

 characters have already been given under the subfamily. Inter- 

 nally the esophagus is long and nearly parallel with the body axis; 

 stomach passing insensibly into the intestine and that into the rec- 

 tum, the entire tube lined with digestive cells filled with black gran- 

 ules; supra ganglion comparatively small, infra ganglion very large 

 and stout and extending back into the genital segment; testes paired, 

 but not always side by side, situated in the head and anterior thorax 

 above the stomach and intestine, spindle-shaped with the sperm 

 ducts leading from their anterior ends back to the large spermato- 

 phore receptacles in the genital segment. 



Type of the genus. — Lcrnaea cyprinacea Linnaeus, first species. 



(Lernaea, Akpvt], a fabled abode of the hydra.) 



Remarks. — In a monograph of this genus by the present author, 

 submitted to the United States Bureau of Fisheries and soon to be 

 published, will be found the complete morphology and life history, 

 together with a full revision of all the known species. 



