350 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



the vitellaria extend to the middle of the acetabulum or even anterior to 

 the acetabulum. 



The elongated specimen from the Atlantic (fig. 21) agreed almost 

 perfectly with one elongated specimen from Pimelometron (not figured) 

 from the Pacific. Variations in the anterior extent of the vitellaria and 

 posterior extent of the cirrus sac in other specimens led to the conclusion 

 that these more elongate specimens did not represent another species. De- 

 cision that specimens from the 3 hosts represented one species was arrived 

 at before relationships of the hosts were considered. It is interesting to 

 note that the 3 host genera are related fishes. 



Opechona pharyngodactyla, new species 

 (Plate 34, figs. 22, 23) 



Host: Trachinotus rhodopus (Gill) (type host) 

 Zalocys stilbe Jordan and McGregor 



Location: Intestine 



Localities: Tenacatita Bay, Mexico (type locality) 



Port Utria, Colombia 



Clarion Island, Mexico 



Number : Several to many 



SPECIFIC DIAGNOSIS OF OPECHONA PHARYNGODACTYLA 



Body flattened, widest near acetabular level but almost equally wide 

 along middle half, anterior end tapering, posterior end broadly rounded. 

 Cuticula with spines which become sparser and scattered posteriorly. 

 Body size 1.714 to 2.903 by 0.397 to 0.487. Oral sucker somewhat longer 

 than wide, 0.102 to 0.126 in transverse diameter. Acetabulum subcircu- 

 lar, about ^ body length from anterior end, 0.146 to 0.187 in diameter; 

 sucker ratio approximately 2:3. Forebody 0.405 to 0.750. Posterior end 

 of oral sucker cupped (calyxlike) in a thin layer of circular muscles. 

 Prepharynx long but retractile so that measurements vary from 0.034 to 

 0.300, flaring at base which often extends down along the side of the 

 pharynx (fig. 23). Pharynx elongate, 0.136 to 0.153 by 0.068 to 0.093, 

 approximately twice as long as wide. Four anteriorly directed, fingerlike, 

 almost transparent, thin- walled processes on anterior end of pharynx (fig. 

 23). These four processes varied considerably in length and might even 

 extend into the oral cavity. The two lateral processes are the largest, and 

 the right seemed always larger than the left. Esophagus and pseudoesoph- 

 agus short, approximately equal, combined length less than pharynx; in- 



