K0.2194. NORTH AMERICAN PARASITIC COPEPODS—niLSON. 33 



1. Trunk straiRlit; all the swimming legs close together and near the head; 



egg cases liliform, straight, and very long; eggs uniseriate; abdomen with 

 n row of feather-like processes on either side Pcnucllinae 11 



2. Head with 2, 3, or 4 soft and swollen horns symmetrically arranged; neck 



and trunk smooth and without transverse grooves, the one passing grad- 

 ually into the other Lcrnaca Linnaeus, 173S, p. 30. 



2. Head with irregular protuberances; neck and trunk transversely wrinkled, 

 the one passing into the other abruptly with a great difference in di- 

 ameter Lcptotrachclus Brian, 1903. p. 40. 



2. Dorsal portion of head extended straight forward, longer than the body, and 



bearing on its swollen tip the antennae; head and trunk the same diame- 

 ter without a nock Thcrodamus Kr0yer, 1SG3, p, 41. 



8. Head and thorax smooth, without processes or horns, and in line with the 

 axis of the trunk Pcnicidus Nordmann, 1S32, p. 44. 



3. Cephalothorax with horns or processes, or both, and often bent at an angle 



with the neck 4 



4. Bilateral symmeti*y perfect ; branched frontal processes covering tlie ante- 



rior head, but no horns or lateral processes; egg strings straight 5 



4. Bilateral symmetry perfect ; lateral horns or cushion-like processes, but no 

 frontal processes; egg strings straight 6 



4. Bilateral synnnetry considerably distorted ; head and neck attached to the 



side of the trunk; egg strings coiled into spirals 7 



5. Cephalothorax and neck straight and attached at right angles to the side of 



the trunk some distance behind the anterior end. 



Peradcrma Heller, 1SG5, p. 49. 



5. Cephalothorax and neck with a sigmoid curve and attached to the anterior 



end of the trunk Cardiodectcs, new genus, p. 50. 



6. Two to ten chitinous horns, or two or three small posterior knobs on the 



cephalothorax; neck not enlarged behind the swimming legs; one pair of 

 maxillae Lcniaccuiciis Le Sueur, 1S24. p. 50. 



6. Two lateral horns on the cephalothorax, soft and unbranched ; neck enlarged 



behind the swimming legs; two pairs of maxillae. 



Sarcotrctes Jungersen, 1911. p. GO. 



7. Neck attached to a lateral anterior corner of the trunk ; abdomen minute and 



hemispherical Phrixocephalus Wilson, 190S. p. 74. 



7. Neck attached to the center of the dorsal surface of. the trunk, abdomen as 



long as the trunk and turned sidewise CoUipravus, new genus, p. 78. 



8. Egg strings looped into loose masses 9 



8. Egg strings coiled into regular tight spirals 10 



9. No abdominal processes; trunk soft and fleshy; cephalic horns very irregular. 



Lcrnacoccra Blainville, 1S22, p. S3. 



9. Five or six branched processes along either side of the abdomen; integu- 



ment of every part of the body thick and chitinized; cephalic horns regu- 

 larly branched 1 Lcrnaeoloplins Heller, ISG-I, p. 89. 



10. Head and neck with lateral processes, simple and soft ; nork rellexed upon 



itself; abdomen two-thirds as long as the trunk and regularly tapered. 

 Ilacmohaphcs Steenstrup and Liitken, ISGl. p. 93. 

 10. Cephalothorax with branched cliitin horns; neck very short and not re- 

 flexed; abdomen as long as the trunk and expanded at the tip. 



Ilacmobaphoidcs T. and A. Scott, 1913, p. 100. 



77403 — Proc.N.M.vol.53— 17 3 



