340 CRUSTACEA 



Key to the suborders of Copepoda: 



Oj The female carries egg sacs 1. EUCOPEPODA 



2 No egg sacs present 2. BRANCIIIURA 



SUBORDER 1. EUCOPEPODA. 



Body elongate; mouth parts biting in the free and sucking in most 

 of the parasitic forms: 15 families. 



Key to the families of Eucopepoda here described: 

 a Free-swimming forms (with a few exceptions). 



& x First antennae 17 to 25-jointed, being very long, usually as long as the 

 body ; but 1 egg sac. 



c x First antennae prehensile in male ; animals marine 1. CALANIDAE 



c a Right first antenna prehensile ; marine and fresh-water animals. 



di First pair of legs normal ; but 1 eye present 2. CENTKOPAGIDAE 



d a First pair of legs weak or rudimentary ; 3 eyes usually present. 



3. PONTELLIDAE 



6 2 First antennae not more than 17-jointed ; usually 2 egg sacs. 

 Cj Abdomen markedly narrower than thorax ; 2 egg sacs ; mostly fresh- 

 water animals 4. CYCLOPIDAE 



c 2 Abdomen not markedly narrower than thorax 5. HABPACTICIDAE 



a, Parasitic forms, but which may usually be free-swimming at times. 

 &! Segmentation distinct. 

 Ci Body with the usual number of segments ; first antennae 5 to 7-jointed. 



C 2 Segmentation indistinct and irregular. 6 * EBGASILIDAE 



di Body wide and flat 7. CALIGIDAE 



d z Body elongate 8. DICHELESTIIDAE 



& 2 Segmentation wanting or. indistinct in the egg-bearing female. 



<?! Legs rudimentary ; proboscis present ; body worm-like 9. LERN^EIDAE 



c a Legs rudimentary or wanting ; no proboscis present ; body worm- 

 like 10. CHONDRACANTHIDAE 



c 3 Legs wanting ; proboscis present ; body thick and sac-like. 



11. LERN^OPODIDAE 



FAMILY 1. CALANIDAE.* 

 Body elongate; first antennae very long, with 

 23 to 25 joints, in the male but slightly modified ; 

 second antennae large and biramose; first 4 pairs 

 of legs biramose, outer branch 3- jointed ; fifth pair 

 either like the preceding or modified and unlike 

 on the two sides; heart present; a single egg sac 

 present : 26 genera, and over 100 species, all marine. 

 1- CALANUS Leach. Thorax composed of 

 either 4 or 5 segments, the last one being some- 

 times asymmetrical; first antennae 25 jointed in 

 the female: many species. 



C. finmarchicus (Gunnerus). Brit (Fig. 532). Length about 4 mm.; 

 color yellowish or reddish, but sometimes absent; thorax of 5 segments; 

 fifth pair of legs biramose ; first antennae as long as the body : New Eng- 

 * See "Copepoda," by W. Giesbrecht and 0, Schmeil, Das Tierreich, 1898, 



