48 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



posterior to bifurcation of esophagus to form intestinal limbs. Ovary 

 in mid-line at posterior part of anterior third of animal, slender in 

 diameter, U-shaped with open end of U pointing posteriorly. Start- 

 ing on the left side the ovary passes forward and winds back and 

 forth laterally about ten times and then turns to the right and passes 

 horizontally across the mid-line and turns abruptly posteriorly and 

 winds horizontally about six times. Oviduct arises from ovary at 

 posterior end of right arm. Vitelline glands from slightly posterior 

 to genital pore to anterior part of posterior third of testicular region, 

 separated anteriorly and posteriorly but confluent between ovary 

 and anterior part of testicular region. Uterus relatively wide and 

 straight. Eggs with anterior and posterior filaments, 0.168 to 0.203 

 mm, in length by 0.072 to 0.080 mm. in width. Anterior and pos- 

 terior polar filaments approximately 0.10 mm. in length. 



Comparisons. H. euthynni is considerably different from any 

 previously described species. It varies particularly in the chitinous 

 skeleton of the posterior suckers. Each sucker has three X-shaped 

 bars parallel to the anterior-posterior axis of the body. The sucker 

 is divided into two portions with a long bar separating the two sides 

 and a short one imbedded in the lateral wall of the sucker on each 

 side. Since this description was made from only one specimen the 

 species is provisional. 



The species name is derived from the genus name of the host, 

 Euthynnus alletteratus (Rafinesque). 



Family: MAZOCRAEIDAE Price, 1936 



Mazocraes macracanthum, new species 



(Plate 6, figs. 25-29) 



Host: Unidentified species of mackerel 

 Location: Gills 



Locality: Tagus Cove, Albemarle Island, Galapagos Is- 

 lands 

 Number: 8 



Body elongated, lanceolate, tapering anteriorly, slightly broader 

 posteriorly, 1.473 to 2.340 mm. in length by 0.356 to 0.474 mm. in 

 width. Posterior haptor relatively large, separated from rest of body 

 by slight constriction, with eight posterior suckers arranged in two 



