164 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 115 



of the fourth thoracic leg-bearmg segment of C. randalli. The sum 

 of the differences between the two species— ^including the differences 

 in the outline of the cephalothorax, the minor differences in the append- 

 ages, and the major differences hsted above — indicate that, thougli 

 the two exhibit many common characteristics and appear to be 

 closely related, they should be considered separately. 



This species is named in honor of Dr. John Randall, whose work 

 (1961) on the biology of the manini, Acanthurus triostegus sandvicensis, 

 the host of the holotype specimen of this copepod, includes a study of 

 the parasites of the fish, 



Caligus ligatus, new species 



Figures Sa-q, 9a-d 



Material. — Adult male (holotype, USNM 105107) taken by 

 author from external surface of specimen of Acanthurus dussumieri 

 Cuvier and Valenciennes captured in fish trap between Diamond 

 Head and Koko Head, Oahu, Hawaii, by Samuel Kaolulo. Immature 

 female (paratype, USNM 105108) taken by author from side of 

 specimen of Naso hexacanthus (Bleeker) collected in fish trap between 

 Diamond Head and Koko Head, Oahu, Hawah, by Samuel Kaolulo. 



Measurements. — Holotype: Length from anterior end of body to 

 posterior end of caudal rami, excluding setae, 2.30 mm. Greatest 

 length of cephalothorax, including frontal region, 1.38 mm.; greatest 

 width, excluding marginal flanges, 1.19 mm. Greatest length of 

 genital segment, excluding setae, 0.41 mm.; greatest width 0.39 mm. 

 Greatest length of abdomen, excluding caudal rami, 0.36 mm. 



Paratype: Length from anterior end of body to posterior end of 

 caudal rami, excluding setae, 2.05 mm. Greatest length of cephalo- 

 thorax, including frontal region, 1.23 mm.; greatest width of cephalo- 

 thorax, excluding marginal flanges, 1.15 mm. Greatest length of 

 genital segment 0.39 mm. ; greatest width 0.38 mm. Greatest length 

 of abdomen 0.31 mm. 



Description. — Male and female with brownish base color in 

 alcohol, with scattered orange-red spots in semi-diamond shape behind 

 eyes, scattered irregularly over rest of cephalothorax, genital segment 

 and third thoracic legs. Eyes red. 



Cephalothorax of male elliptical, frontal region distinct though 

 width less than half that of cephalothorax. Lunules large, extending 

 posteriorly from anterior margin to slightly past junction of frontal 

 region and cephalothorax (fig. 8^). Division between frontal region 

 and cephalothorax distinct, trilobed, median lobe larger than slightly 

 irregular lateral lobes. Lateral margins of cephalothorax with narrow, 

 membranous flange. Posterior sinuses distinct, narrow, U-shaped, 

 with small, membranous flange on outer margin. Median cephalo- 



