338 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



Bucephalus introversus, new species 



(Plate 3 2, figs. 10-12) 



Hosts Locality Number 



(Type) Seriola species Port Culebra, Colombia 11 



Seriola dorsalis (Gill) Port Utria, Colombia 15 



Seriola dorsalis Isabel Island, Mexico 1 



Seriola durnerili (Risso) White Friar Islan.!>, Mexico 3 



Caranx hippos (Linn.) Port Culebra, Colombia 1 



Location : Stomach. Once on the gills, never in the intestine 



SPECIFIC DIAGNOSIS OF BUCEPHALUS INTROATRSUS 



Body elongate, cylindrical, blunt at anterior end, rounded and little 

 tapering at posterior end. In almost all specimens the anterior end was 

 introverted into the anterior part of the body for a distance often Yz and 

 sometimes almost >4 body length. Four specim.ens with anterior end 

 everted measured 1.202 to 1.707 in length and 0.225 to 0.285 in thick- 

 ness. Anterior sucker muscular with ventral aperture. Dorsal wall of 

 sucker rhynchuslike with 5 or 6 distinct longitudinal bruhis of diagonal 

 muscles (or glands ?). When inverted, the anterior sucker resembles 

 still more a rhynchus, since the aperture of the sucker is not evident.. 

 Seven tentacles usually completely retracted. Tentacle long and narrow 

 (fig. 12), with a single large basal process near the base. Diameter of 

 anterior sucker 0.170 to 0.345. Mouth normally posterior to midbody 

 (1.035 from anterior end in a 1.707 specimen; 0.817 in a 1.202 speci- 

 men). Even when the anterior end is well inverted, the mouth is usually 

 posterior to midbody but under these conditions may be nearer the ap- 

 parent anterior end. Pharynx variable, usually longer than wide, 0.037 

 to 0.061 in width. Intestine dorsal and slightly anterior or posterior to 

 mouth. Gonads tandem, to the right, just posterior to pliarynx. Testes 

 large, spherical, tandem, close together. Cirrus sac large, J j body length 

 or often somewhat more; its base overlaps (to the left) at least the pos- 

 terior testis and may reach to ovary, containing an elongate-oval seminal 

 vesicle, long pars prostatica, and large prostate gland. Genital atrium 

 with a complicated sj^stem of lobes and folds (fig. 10) ; atrial tube vari- 

 able in shape and length, its circular muscles sometimes conspicuous. 

 Genital pore close to posterior tip of body, verj^ close to excretory pore, 

 which is, however, separate. Ovary spherical, pretesticular, about at 

 pharynx level. Vitellaria in 2 lateral groups, more or less clumped, ex- 

 tending anterior and posterior to phaiynx a short distance. Follicles on 



