NO. 14 MANTER : DIGENETIC TREMATODES OF FISHES 415 



except for the fact that its members are from fishes." They consider 

 Cryptogoniminae a synonym of Heterophyinae. The writer agrees with 

 this conclusion. 



These opinions suggest a similarity between the Acanthostomidae 

 and the Heterophyidae. Such a similarity does seem to exist, and a re- 

 alignment of the two families in relationship to each other is needed. 

 Acanthostomidae is perhaps a heterogeneous group, some of the genera 

 in it (e.g. Maesnia Chatter] i, 1933 and Anoiktostoma Stossich, 1899) 

 apparently possessing a cirrus sac. Most of the genera listed in the Acan- 

 thostomidae could be logically placed in the Heterophyidae. It seems 

 probable that too much emphasis has been placed on an oral crown of 

 spines and not enough consideration given to the terminal genital struc- 

 tures and posterior extent of the uterus. Perhaps knowledge of life cycles 

 will be necessary to elucidate the status of the two families. 



Mueller and Van Cleave recognized six subfamilies of the Hetero- 

 phyidae. Manter (1934, p. 325) considered Siphodera and Siphoderina 

 in a new subfamily Siphoderinae. It seems apparent, however, that Sipho- 

 dera, Siphoderina, Cryptogonimus, Paracryptogonimus, Centrovarium, 

 Biovarium, and Caecincola are similar enough to be classified in one sub- 

 family. Paracryptogonimus, in particular, shows relationship to Neo- 

 chasmus and Allacanthochasmus in its oral spines, deeply lobed ovary, 

 and posterior uterus, differing in lacking a gonotyl. But the presence or 

 absence of a gonotyl has not been considered a subfamily character. The 

 plate of heterophyid genera given by Mueller and Van Cleave (1932, 

 pi. 25, p. 129) shows a series in which Paracryptogonimus and Siphodera 

 might well fit. Mueller and Van Cleave consider the oral spines a sub- 

 family distinction between Heterophyinae and Neochasminae. Since these 

 spines are absent or present in marine trematodes as closely related to 

 each other as Siphoderina and Paraciyptogonimus, they do not seem to 

 constitute more than a generic difference. 



Yamaguti (1938) has recently discussed certain Japanese trematodes 

 in the genera Exorchis Kobayashi, 1921 and Pseudexorchis Yamaguti, 

 1938. His subfamily Exorchiinae is essentially similar to Siphoderinae 

 and hence should also be considered a synonym of Heterophyinae. In 

 this connection it might be noted that the cercaria of Pseudexorchis major 

 (Hasegawa, 1935) "resembles the cercaria of Metagonunus yokogawai 

 so closely that even an experienced trematologist might be unable to dis- 

 tinguish the two without experimental evidence." 



