TREMATODE PARASITES. 103 



although only one is quoted in the literature since the establishment of the 

 genus Gorgodera for Distomum cygnoides, ZED. = Pleorchis cygnoides, STOSS. This 

 only species is Pleorchis poly orchis (STOSS.), an intestinal parasite of the Mediterranean 

 Corvina nigra. To the same species LINTON has referred an intestinal parasite of 

 the North-American Cynoscion regalis, which I regard as a different species and 

 which I will name Pleorchis americanus, n. sp. Besides the different habitat, the 

 two species differ from each other in several important points of their anatomy ; 

 a distinct oesophagus is wanting in PL polyorchis, but present in PI. americanus, 

 and the anterior branches of the intestine are short and run parallel to the main 

 branches in PL polyorchis, but are somewhat longer and form an angle with the 

 larger intestinal coeca in PL americanus. In the latter species, moreover, the size 

 of the two suckers seems to be smaller than in PL polyorchis (according to the 

 figures given by STOSSTCH and LINTON), and the number of testes somewhat larger 

 than in PL polyorchis, which, according to STOSSICH, is provided constantly with 

 24 testes, whilst LINTON has counted 26 to 30 in Pleorchis americanus. It is of 

 interest, that in this species also, as in Gorgodera and in Sinistorchis, the number 

 of the testes is different on the two sides. In one specimen only LINTON found 

 15 testes on each side, and in another 15 on the right and 12 on the left, while 

 of nine specimens with 14 testes on the right, two were provided with 16, three 

 with 15, two with 13, and two with 12 testes on the left. 



Gastris, n. gen. 



Provisional generic diagnosis. Distomids of large size, with a very muscular body, 

 without spines. Anterior part of the body, between the two suckers, ventrally 

 excavated ; posterior part of the body, behind the ventral sucker, broadened, oval- 

 shaped. 



Oral sucker subterminal ; pharynx well developed ; oesophagus short ; intestinal 

 cceca long, and finishing not very far in front of the posterior end of the body. 



Excretory system U-shaped, with long branches, situated between the intestinal 

 coeca. Genital opening about midway between the two suckers, in the median line. 

 Cirrus-pouch large, oval-shaped, situated in the angle between the two intestinal 

 coaca. 



The two testes globular, situated nearly symmetrically side by side, touching 

 laterally the intestinal coeca and separated from each other by the uterus. Ovary in 

 front of the testes near the median line. Yolk glands in the posterior half of the 

 body, laterally to the intestinal coeca, arranged in several (6 to 7) groups, which lie 

 behind each other and are separated from each other by a small interspace, in the 

 same manner as in the genus Opisthorchis, R. BL. Uterus running at first to a 

 little extent forwards, but turning very soon, proceeding then posteriorly and reaching 

 the level of the blind ends of the intestinal coeca, not extending laterally beyond the 



