INTERNAL PARASITES OF THE SEBAGO SALMON. II85 



from various parts of Europe. Of its occurrence in the Rhine salmon, where it 

 is found in 42 per cent of the specimens examined, in 91 per cent of the Baltic 

 salmon, in 26 per cent of the Tweed salmon, in most of the Tay salmon and of 

 the Irish salmon, enough has been said in the historical surv^ey. It is a typical 

 salmonid parasite, and is found even in eight species of that family which inhabit 

 fresh water. Its presence in the landlocked Salmo schago, which confines its 

 life cycle to fresh water, is hence not surprising. Evidentlj^ the life cycle of the 

 species permits of easy adaptation to a fresh-water existence, for I have to report 

 its occurrence not only in the host under discussion, but also in another promi- 

 nent American salmonid, the Great Lakes trout, Cristivomer namaycush (Wal- 

 baum). It was found abundantly in specimens of this host which I examined 

 in July and August, 1894, at Charlevoix, Mich. From 30 to 80 tapeworms of 

 this species were present in each Sebago salmon, and neither size nor age played 

 any evident part in determining the degree of infestation. Absolutely every 

 one of the salmon taken was infested. In considering the possible life history, 

 I naturally turned to the Sebago smelt as the host of the larval form, probably a 

 plerocercoid, and examined a number of these fish with great care, but was 

 unable to detect the lar\'a, if indeed it was present. Nothing was discovered 

 which throws any light on the life cycle. It is worthy of note that all of these 

 parasites were full grown; not a single specimen was found which was not dis- 

 charging ripe proglottids. Consequently the infestation must have taken place 

 somewhat earlier in the year. It would take observations at other months to 

 determine when; and the food at that time would evidently be the source of 

 the parasite. 



In addition to this dominant species some other cestodes were also recorded. 

 A few fragments of a small species of Proteocephahis were found in each of four 

 hosts, and a larval form, which probably belongs to the same Proteocephalus, 

 was obtained in each of two hosts. Two different bothriocephalid larvae of 

 small size also occurred each in a single salmon. The four forms just mentioned 

 were all found in the intestine. 



The insignificant size of a new species of Proteocephalus found and the small 

 number of individuals present in any one host resulted in its being overlooked 

 at first, and it may easily have been present in more hosts than shown by the 

 records. It was found in four out of the seven salmon examined, but in one 

 case only a few loose proglottids were discovered by accident among material 

 from the intestine. A careful examination in comparison with the descriptions 

 of known species leads me to the view that this is a new species to which the 

 name Proteocephalus pusillus may be given. The salient points in the descrip- 

 tion of this new species are as follows: 



Proteocephalus pusillus nov. spec. — Adult cestode with short strobila, meas- 

 uring only 30 to 50 mm. in length. Proglottids scanty, segmentation 



