COPEPODS OF THE WOODS HOLE EEGION 539 



KEY TO THE SUBORDERS 



1. A movable articulation between third and fourth thoracic seg- 



ments; body more or less depressed; parasitic or free swim- 

 ming 2 



A movable articulation between fourth and fifth thoracic seg- 

 ments; body depressed or cylindrical; parasitic, commensal, 

 free swimming, or benthonic 3 



A movable articulation between fifth and sixth thoracic seg- 

 ments; body more or less depressed; free swimming only. Calanoida (p. 540) 



Body rigidly fused, without a movable articulation, often with- 

 out segmentation; fixed parasites only 6 



2. No second antennae or mouth parts; parasitic during develop- 



ment and free swimming in adult stage Monstrilloida (p. 604) 



Both second antennae and mouth parts present; free swimming 



during development, parasitic in adult stage Caligoida (part) (p. 604) 



3. Fifth and genital segments fused with abdomen and without 



segmentation; no fifth or sixth legs; parasitic Arguloida (p. 539) 



Fifth and genital segments distinctly separated; abdomen seg- 

 mented; fifth and often sixth legs present 4 



4. Urosome about as wide as metasome and both more or less 



cylindrical; basal segment of fifth legs with inner expansion. 



Harpacticoida (p. 560) 

 Metasome much wider than urosome and depressed; basal seg- 

 ment of fifth leg without an inner expansion 5 



5. First antennae usually elongate, prehensile or often not prehensile 



in male; eggs carried in lateral ovisacs Cyclopoida (p. 583) 



First antennae short, with few segments, always prehensile in 



male; eggs carried in dorsal ovisacs Notodelphyoida (part) (p. 598) 



6. Body rigid in both sexes; female a fixed parasite, male a pygmy 



attached to female Lernaeopodoida (p. 613) 



Body rigid in female only; male neither a pygmy nor attached 



to female, but belonging in 2 or 5 above 7 



7. Eggs carried in external ovisacs; body depressed; external para- 



sites of fishes, etc Caligoida (part) (p. 604) 



Eggs carried in a dorsal brood-pouch; body compressed; com- 

 mensal in ascidians, etc Notodelphyoida (part) (p. 598) 



KEY TO THE GENERA OF THE SUBORDER ARGULOIDA 



1. Carapace orbicular, ovate, or elliptical; maxillipeds armed with 



a basal plate; caudal rami present 2 



Carapace drawn out into elongate lateral wings; no basal plate 



on maxillipeds; no caudal rami 4 



2. Second maxillae transformed into prehensile disks 3 



Second maxillae normal, tipped with curved claws; no preoral 



sting in front of mouth cf 9 Dolops Audouin, 1837 



3. Two pairs of antennae; preoral sting present; basal plate of maxil- 



lipeds armed with teeth cf ? Argulus Miiller, 1785 (p. 12) 



One pair of antennae; no preoral sting; basal plate of maxillipeds 



without teeth 9 Chonopeltis Thiele, 1901 



4. Rudiments of 2 pairs of antennae and a preoral sting; wings 



reaching beyond tip of abdomen 9 Dipteropeltis Caiman, 1912 



Antennae and preoral sting lacking; wings scarcely reaching base 



of abdomen 9 Talaus Moreira, 1913 



