LEPEOPHTHEIRUS THOMPSOXI. 69 



4. Lepeophtheirus thompsoni Baird. 



(Plate XVII, fig. 3 ; Plate XXV, fig. 10 ; Plate 

 XL VIII, figs. 1-3.) 



1850. Lepeophtheirus thompsoni Baird. (4) p. 278, pi. xxx, fig. 2. 



1851. Caliyus gracilis P. J. van Beneden. (11) p. 90, pi. ii, figs. 1-7. 

 1861. Caligus branchialis Malm, mscr. ? Steenstrup & Liitken. 



(127) p. 362, pi. ii, fig. 3. 



1863. Lepeophtheirus rhombi Kroyer. (71) p. 118, pi. v, fig. 5. 



1885. Lepeophtheirus grucilis Carus. (29a) Prodr. Faunae Mediter- 

 raneae, p. 359. 



1900. Lepeophtheirus thompsoni T. Scott. (112) p. 152, pi. v, figs. 

 43-45. 



1900. Lepeophtheirus obscurus idem. (112) p. 153, pi. vi, figs. 16-19. 



19()5. Lepeophtheirus thompsoni C. B. Wilson. (145) p. 619. pi. xviii, 

 figs. 21-2-219. 



Female. Carapace suborbicular and equal in length 

 to about two-fifths of the entire length of the animal. 

 Frontal plates arcuate, and tolerably prominent. Free 

 thoracic segment small. Genital segment large and 

 nearly as long as the carapace, widest at the distal end, 

 which is about three-fourths the width of the cara- 

 pace, but the width gradually decreases anteriorly to 

 where the proximal end rapidly contracts to form a 

 narrow neck ; lateral margins slightly arcuate, or 

 nearly straight, postero-lateral corners somewhat pro- 

 duced into broadly-rounded lobes. Abdomen toler- 

 ably elongated and equal to about two-thirds the 

 length of the genital segment, a slight constriction 

 near the posterior end giving it the appearance of an 

 indistinct joint. Caudal rami short. 



Antennules about two-thirds the length of the frontal 

 plates. Antennae rather slender. Second maxillipeds 

 tolerably stout. Sternal fork robust with the rami 

 somewhat expanded, widest in the middle and tapering 

 slightly towards each end, also moderately far apart 

 and scarcely divergent. Fourth pair of thoracic legs 

 small, basal joint tolerably stout, and with the ramus 

 composed of three joints, the outer distal angle of the 

 first joint forming a blunt-pointed knob, that of the 

 second joint bearing a small spine, the third armed 

 with one short and two moderately long and spiniform 

 apical setae. Fifth pair minute. Length about 8'5 mm. 



