350 



CBUSTACEA 



ring on the cod, flounder, and more than 25 other kinds of marine 

 fishes. 



2. Lepeophtheirtjs von Nordmann. Similar to Caligus but with 

 out the suckers: 12 American species. 



L. edwardsi C. B. Wilson (Fig. 552). End segment 

 less than half as long as the genital segment and 

 1-jointed; length of female about 7 mm.: on flounders 

 and other fish. 



Family 8. DICHELESTIIDAE. 



Body usually' elongated and flattened, with segmen- 

 tation partially obliterated; first antennae delicate and 

 usually many-jointed; second antennae in form of long 

 hooks; hinder pair of legs usually reduced: about 20 

 genera and 60 species, which are parasitic on fishes, 

 principally selachians. 



DiCHELESTiUM Hermann. First 2 pairs of legs 

 small and biramose, third pair broad and plate-like, 

 fourth and fifth wanting; first antennae 8-jointed : 3 spe- 

 cies, in fresh and salt water. 

 D. sturionis Herm. Length 2 cm.: on the gills of sturgeons; Vine- 

 yard and Long Island Sounds. 



Fig. 552 



Lepeophthei- 



rus edwardsi 



(Wilson). 



Family 9. LERN^IDAE. 



Body very different in form at different periods ; during the breeding 

 period the animals swim about freely, and the body consists of a large 

 cephalothorax, a thorax bearing 4 pairs of biramose legs, and an elongate 

 abdomen; after fertilization the female changes into an unsegmented, 

 worm-like creature with minute legs and projections at the forward end 

 representing the antennae, and with a pair of egg sacs projecting from 

 the hinder end; the front end is imbedded in the body of the fish on 

 which it lives: about 50 species. 



1. LERNiEA L. The pairs of legs of the swimming individuals close 

 together; body of egg-bearing female twisted S-shape, with a pair of 

 egg sacs. 



L. brancliialis L. Length extended, 4 cm. ; egg sacs convoluted : on 

 the gills of the cod and other fishes. 



2. Lerne^nicus Lesson. Legs of the swimming forms much re- 

 duced and close together; body of adult female elongated, with long 

 egg sacs. 



L. radiata Les. (Fig. 553). Length 4 cm.: on the menhaden; 

 common. 



