27 



Leg 5 (fig. 137) located at beginning of distal third of genital segment 

 and consisting of a ventral lobe bearing 1 outer pluniose seta, a group 

 of 2 plumose setae and a naked spine at distal end of lobe. Leg 6 

 (fig. 138) located on posterior border of genital segment near junction 

 of abdomen and consisting of an outer plumose seta and an inner 

 naked spine. 



Discussion. — Phyllothereus cornutus is a parasite on the gills and 

 gill arches of a number of species of sharks, but it is most commonly 

 found associated with Prionace glauca. It is cosmopolitan in distribu- 

 tion and has been collected by the author in both the Indian Ocean 

 and the North Atlantic. The Indian Ocean specimens were smaller 

 than those collected in the North Atlantic, but a detailed examination 

 of theii' appendages showed no important differences. Since the same 

 host was involved in both cases, I have concluded that they are of 

 the same species. More collections in intermediate areas might weU. 

 yield intermediate sizes. The nature of the inflated dorsal plates 

 seems to be a function of the preserving fluid (70 percent alcohol or 

 10 percent formalin) as this condition has not been observed by me 

 in life. 



Genus Gangliopus Gerstaecker, 1854 



Gangliopus Gerstaecker, 1854, p. 189. [Type-species: G. pyriformis.] 



Female.— Frontal plate distinctly separate. Fu'st thoracic segment 

 fused with cephalon. Thoracic segments 2-4 free and possessing 

 dorsal plates. Dorsal plates of segment 2 small. Plate of segment 3 

 extending beyond tip of plate of segment 2. Plates of segment 4 

 partially separated. Abdomen 1-segmented, with a dorsal plate. 

 Abdomen or its plate visible dorsally and attached to distal end of 

 genital segment. Caudal rami lateral to abdomen. Fu'st antenna 

 2-segmented. Claw of maxilliped pointed at tip. Adhesion pads of 

 the first and second antenna absent or reduced. Pad of maxilliped 

 well developed. Legs 1-4 biramose, rami of legs 1-3 2-segmented, 

 those of leg 4 1-segmented. All legs without plumose setae. Leg 5 

 present. Egg sacs long and held straight. 



Male. — No dorsal plates present. Cephalic appendages like those 

 of female. Adhesion pad with first antenna. Legs 1-4 biramose, 

 all rami 2-segmented and bearing plumose setae. Fifth and sixth 

 legs present. Leg 3 endopod unmodified. Caudal rami held at 

 distal end of abdomen. 



