153] PROTEOCEPHALIDAE—LA RUE 153 



and in one of the infested gars the P. perplexus was not accompanied 

 by any other species of Proteocephalus. In two of the gars P. singu- 

 laris occurred together with P. perplexus. Nothing is known regarding 

 the seasonal distribution of the parasite and almost nothing regarding 

 its geographical distribution. It has not been found in the Amia of the 

 Great Lakes which Professor Ward examined a number of years ago. 

 In those specimens were found P. ambloplitis. 



Judging from external appearances alone these specimens of P. 

 perplexus are very much like specimens of P. ambloplitis. Even after 

 staining and mounting some pieces in toto they appear to belong to 

 that species tho certain points of difference may be indistinctly made 

 out. Examination of sections revealed certain characters by which the 

 two species may be differentiated. The writer (1911:478) proposed the 

 name Proteocephalus perplexus for this species by reason of the diffi- 

 culties attending its differentiation from its nearest congener. In size 

 P. perplexus is somewhat smaller than P. ambloplitis. Its strobila is 

 shorter, narrower and thinner. Its head is a little smaller than that 

 of P. ambloplitis but is very similar in shape and it has four grooves 

 as does that species. Sometimes the minute papilla at the apex of the 

 head thought to be characteristic of P. ambloplitis may be seen. The 

 suckers are large and in a position similar to that which they occupy in 

 P. ambloplitis. 



The head (Fig. 17) is somewhat spheroidal. It is flattened dorso- 

 ventrally and is evenly rounded anteriorly. Four grooves extend from 

 the base of the head nearly to the apex where frequently there is a 

 small papilla in a shallow depression. The head is not as truncate as 

 the head of P. ambloplitis described by Benedict (1900). It resembles 

 very closely heads which the writer has examined and drawn (Figs. 18, 

 19) of the latter species. Four heads of P. perplexus measured in 

 breadth and length 0.663 by 0.510 mm., 0.697 by 0.425 mm., 0.697 by 

 0.510 mm., 0.714 by 0.459 mm. The suckers measured 0.340-0.459 mm. 

 long by 0.255-0.272 mm. broad. There is no fifth sucker and no rostel- 

 lum. Sections through the apex of the head failed to reveal even a vestige 

 of a fifth sucker. In P. ambloplitis the rudimentary fifth sucker is 

 large. The suckers are deep and well muscled, usually longer than 

 broad. The sucker-opening is directed outward and slightly forward. 

 The neck is 0.5-0.6 mm. long. It is broad and thick but narrower than 

 the head. No complete strobila was found yet most of the longer pieces 

 contained ripe proglottids. Six pieces with heads measured 65, 91, 106, 

 105, 125, and 155 mm. long respectively. The maximum breadth ob- 

 served was 1.7 mm. 



