because in the work of Price there are no indications whatsoever on the 

 subject and in addition he correctly considers it impossible to recognize 

 the representatives of Perciformes as the host of S. mavori and supposes 

 that such (the host, nobis ) must be some shark, hence the necessity of 

 excluding the species under consideration from the group of those which 

 parasitize representatives of two different orders of fishes and to transfer 

 it into the group with one host. 



In conclusion of our analysis of the 18 species of monogenetic 

 trematodes indicated as parasitizing different orders of fishes one raust 

 exclude as incorrectly placed in this group of species the following: 



(1) Diclidophora palmata (Leuckart), Tristoma integrum 

 Diesing, Squalonchocotyle mavori (Linton), and Cyclocotyla bellones Otto-- 

 actually they appear only on one species of host; 



(2) Calicotyle kroyeri Diesing is encountered only on repre- 

 sentatives of one genus of fishes; 



(3) Diclidophora merlangi (Kuhn) parasitizes representatives 

 of two genera of one family of fishes or even one species. 



Further one must consider the relation of the following four 

 species to the given group as doubtful: Ancyrocephalus alatus Chauhan, 

 Squamodiscus belengeri Chauhan, Bilaterocotyle chirocentrosus (Chauhan) 

 and Urocleidus mimus Mueller. The first three are described by Chauhan 

 and his data about the hosts are doubtful and require special verification. 

 With a great degree of probability , one can consider that Squamodiscus 

 belengeri and Bilaterocotyle chirocentrosus p arasitize only Sciaenidae and 

 are encountered only accidentally on other hosts. As regards Urocleidus 

 mimus, the latter species apparently is encountered only on one species 

 of host, which agrees with the subsequent data as we will see further 

 (see page 350 ). 



Four species are encountered on fishes which are related in 

 some degree, althoxigh belonging to different orders: Benedenia melleni 

 (MacCallum), ? Diplectanotrema balistes (MacCallum), Dionchus remorae 

 (MacCallum), and Microbothrium apiculatum Olsson. One can consider 

 as linked to this group the two species of Tristoma examined here-- Tr. 

 coccineum Couvier and Tr. papillosum Diesing of which each is encountered 

 on two closely related families of Perciformes and on one family of 

 Tetrodontiformes, which are undoubtedly linked phylogenetically with the 

 preceding order, although somewhat remotely. Finally only two species 

 are encountered on orders of fishes unrelated to each other, specifically-- 

 Calicotyle affinis Scott and Gyrodactylus arcuatus Bychowsky, We will 

 return later to these two species. 



253 



