NO. 14 MANTER: DIGENETICTREMATODES OF FISHES 333 



great detail and contrasted the genus Prosorhynchus with Gasterosto- 

 mum (now Bucephalus) chiefly on the structure of the anterior end 

 which bears in Prosorhynchus a "rostellum-like structure" called the 

 rhynchus. Nicoll later (1914) elevated these differences to subfamily 

 rank, recognizing Prosorhynchinae (with a rhynchus) and Bucephalinae 

 (with an anterior sucker). Although Eckmann (1932) does not recog- 

 nize subfamilies of the Bucephalidae, the subdivision seems a convenient 

 one and is followed by Nagaty (1937). 



In recent years gasterostomes have received considerable attention, 

 and the number of species in the relatively few genera has increased 

 rapidly. There is disagreement among authors as to the validity of a 

 number of species and a few genera, but this confusion normally accom- 

 panies the early taxonomic history when a group is being rapidly de- 

 veloped. The following recent authors have contributed materially to 

 our knowledge of the group: Ozaki (1928), Eckmann (1932), Verma 

 (1936), Bhalerao (1937), and Nagaty (1937). 



The genus Bucephalus possesses a ventrally directed sucker with defi- 

 nite radial muscles, aperture, and cuplike cavity together with a crown 

 of retractile processes known as fimbriae or tentacles. These curious ap- 

 pendages, conspicuous when extended but very inconspicuous when re- 

 tracted, have come to be the characteristic feature of the genus, vaiying 

 in number and form in different species. When extended, they often re- 

 semble horns. It is a curious circumstance that the generic name Buceph- 

 alus (= ox head), given to the cercaria because of the hornlike appear- 

 ance of the furcae of the tail, should prove to be appropriate for the 

 adult because of entirely different structures. 



Some confusion might arise in recognition of the genus Bucephalus 

 because of failure to note the presence of tentacles when these are com- 

 pletely retracted. Under such conditions the tentacles are evidenced only 

 as small papillae of which the most ventral (on each side of the aperture 

 of the sucker) or the lateral pair is likely to be most conspicuous. Study 

 of these protuberances will reveal a central porelike depression. Rhipi- 

 docotyle kathetostomae Manter, 1934 shows what is now familiar to 

 the author as characteristic retracted tentacles, and its name is here 

 changed to Bucephalus kathetostomae (Manter) n. comb. Although the 

 shape of its tentacles remains unknown, the species can be distinguished 

 from others in the genus Bucephalus. Van Cleave and Mueller (1934) 

 considered the appearance of the tentacles in Bucephalus elegans Wood- 

 head an indication of age or senescence. While immature individuals may 



