2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 78 



arcuatus. Black angel fish. Aq. Jany. 13, '17"; and 1 specimen, a 

 toto mount stained with carmine (U.S.N.M. No. 8091), labeled 

 " Monostomum fomacantlii^ int., PoTnacanthus paru. Aq. Ap. 18, 

 '17." All of these specimens show evidence of having been flattened 

 before fixation and certain details can not be made out. The meas- 

 urements given in the following description are doubtless consider- 

 ably in excess of what they would have been had a different technique 

 been followed in the handling and preserving of the specimens. 



PLEUROGONIUS POMACANTHI (MacCallum. 1916) 



Synonym. — Monostomum pomacanthi MacCallum, 1916. 



Specific description. — Pleurogonius: Body elongated, 3.5 to 6 mm. 

 long by 1.25 to 2 mm. wide in the region of the ovary ; anterior end 

 bluntly pointed and posterior end rounded. A short distance caudad 

 of the oral sucker, the ventral surface shows a deep depression over 

 which project two shoulderlike structures, one on each side, which 

 are not connected dorsally by a ridge as in Pronocephalus and 

 related genera. The cuticle is smooth and without spines. The 

 oral sucker is terminal, 153//, to 236/a in diameter; esophagus 310/x 

 to 465ju, long; intestinal ceca extend to posterior end of body, the 

 posterior portions bending medially, passing between the testes, and 

 provided with pocketlike diverticula throughout their entire length. 

 The excretory pore is oval in outline and situated dorsally near the 

 posterior end of the body, but owing to the extreme flattening of the 

 specimens the remainder of the excretory system can not be made 

 out. The genital pores are close together, 1.5 to 2.5 mm. from the 

 anterior end, and situated near the margin on the left side of the 

 body. The testes are ovoid, 524|u to 620/x long by 356/* to 387/i wide, 

 with irregular outline, situated near the posterior end of the body 

 and separated from each other by the terminal portions of the ceca. 

 The cirrus pouch is from 0.93 to 1.5 mm. long by 155/* to 310/t wide 

 and directed obliquely backward; it is strongly muscular and con- 

 tains a well-developed prostate and a simple, unarmed cirrus. The 

 seminal vesicle is strongly convoluted and lies free in the parenchyma 

 at the base of the cirrus pouch. The ovary is more or less triangular 

 in outline, 310/a to 520/i long by 232/i to 248/* wide, pretesticular, and 

 situated to the right of the median line. The shell gland is about 

 one-half the size of the ovary and lies in the median line caudad of 

 the ovary. The vitellaria consist of ovoid follicles and are situated 

 immediately anterior to the testes. (The masses which are shown in 

 MacCallum's (1916) figure of this species, lying in the extreme pos- 

 terior end and in the anterior half of the body, and described as 

 vitelline follicles, are intestinal diverticula filled with ingesta.) The 



