No. 2194. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 81 



Remarks. — In the material collected by the Bureau of Fisheries 

 steamer Albatross there were three specimens which had been re- 

 moved from their host and two which were still attached, one on 

 either side, to the gills of a JenJdnsia stolifera 40 mm. long. As 

 is usual in such cases the torsion in these parasites was in opposite 

 directions, as was also the flexion of the abdomen. On dissecting 

 out the parasites their necks were found to enter the ventral aorta of 

 the host at about the same point, just in front of the two arteries 

 that supply the posterior gill arch. Both necks turned backward 

 inside the aorta and the heads of the parasites w^ere found closely 

 packed together and filling the entire cavity of the bulbus arteriosus. 



One head {a) was superimposed upon the other (Z;), the dorsal 

 surfaces of the two facing the ventral wall of the aorta and the 

 ventral surface of {a) packed against the dorsal surface of {h). 

 The head (a) was longer than (&), thus bringing its anterior ven- 

 tral surface with the mouth-tube in front of the frontal margin of 

 (&). Both mouths w^ere thus unobstructed and could take in blood 

 freely; the free anterior end of («) w^as inflated into a cylinder 

 the full size of the lumen of the bulbus, the remainder of («) and 

 the whole of {h) were much flattened dorso-ventrally. 



This leads to the conclusion that under normal conditions, when 

 there was but a single head inside the bulbus, its form would be 

 cylindrical and but little flattened. Both heads have been used in 

 the details here presented, and in the figures a dorsal and lateral 

 view of (a) (figs. 90 and 91) and a dorsal and ventral view of {h) 

 (figs. 92 and 93) are given. 



How the tiny fish could live and apparently thrive with two such 

 parasites literally sucking its heart's blood is a mystery. 



The genus can be easily recognized by the flexion of the com- 

 parati^ely large abdomen and by the misplacement of the neck on 

 the dorsal surface of the trunk. The complete distortion of bilat- 

 eral symmetry in the internal morphology follows as a result of 

 tills misplacement. 



Lernaeocerinae, new subfamily. 



Subfamily characters of female. — Cephalothorax armed with hard 

 chitin horns, more or less branched ; neck and trunk curved, usually 

 in the shape of the letter S; genital segment enlarged; no pre- 

 genital prominence but often lateral processes over the bases of the 

 egg strings; the latter filiform, very long and coiled in loose masses 

 or twisted into a tight and regular spiral; eggs uniseriate and 

 packed like a row of coins. 



Two pairs of antennae, second pair chelate; manibles unknown; 

 no protrusible proboscis; two pairs of maxillae, second pair uncinate; 

 77403— Proc.N.M.vol.53— 17 6 



