380 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



Plagioporus gastrocotylus, new species 

 (Plate 39, figs. 61-63) 



Host: Calamus brachysomus (Lockington) 

 Location: Intestine 

 Locality: Charles Island, Galapagos 

 Number: 7 specimens in one host 



SPECIFIC DIAGNOSIS OF PLAGIOPORUS GASTROCOTYLUS 

 Body plump, smooth, fusiform, tapering toward each end from the 

 wide acetabular region, greatest width more than half body length. Size 

 L485 to 2.686 in length by 0.862 to 1.377 in greatest width. Oral sucker 

 slightly extended at posterior end, slightly longer than wide, 0.232 to 

 0.352 in transverse diameter; acetabulum, located at about midbody, 

 somewhat wider than long, with transverse aperture, 0.412 to 0.585 in 

 transverse diameter. Sucker ratio almost 1 :2. Ventral surface of widest 

 portion of body almost wholly enclosed by a large circular fold of body 

 wall which leaves an aperture opposite acetabulum of about the size of the 

 acetabulum (figs. 62 and 63). Lateral portions of this fold not separated 

 from body surface but anterior edge and often the posterior edge clearly 

 demarked. (This curious overlapping sheet of the body wall is the most 

 unique characteristic of the species.) 



Prepharynx lacking ; phaiynx large, either wider than long or longer 

 than wide, 0.165 to 0.292 in length, 0.150 to 0.285 in width; esophagus 

 lacking or very short; intestinal bifurcation about midway between suck- 

 ers; ceca wide, extending to near posterior end of body. Genital pore 

 median or submedian, usually opposite middle of pharynx, sometimes op- 

 posite base of pharynx. Testes smooth, subspherical, close together, diago- 

 nal, intercecal, in middle of hindbody, anterior testis slightly sinistral, 

 posttesticular space 0.090 to 0.270. Cirrus sac claviform, elongate, from 

 genital pore to about midacetabular level; cirrus long and slightly sinu- 

 ous ; seminal vesicle internal, coiled, surrounded by prostatic cells. Ovary 

 spherical, to the right, immediately posterior to acetabulum, overlapped 

 by body fold; Mehlis' gland at anteroleft border of ovary; seminal recep- 

 tacle large, partly dorsal and partly posterior to ovary; Laurer's canal 

 present ; uterus chiefly to left of ovary, extending backward to overlap an- 

 terior testis, reaching almost to anterior border of posterior testis. Eggs 

 thin shelled, 63 to 68 by 32 to 37 /x. Vitellaria from mid-pharynx level to 

 posterior end of body, surrounding ceca except on inner sides, confluent 

 posterior to testes, not extending into ventral fold of body wall. Excre- 

 tory vesicle extending forward to ovary. 



