Trematode Parasites of British Birds. 2()9 



III couuection with the above described three species it is 

 interesting to read Jagerskicild's note^ in which he says : — 

 " During my search for Leviasenia brachysoma I have found 

 that there are quite a number of small Distomids, having 

 the habitat of a Levinsenia, but so different in their copulatory 

 organs that we are compelled to assign them to other genera. 

 Thus, for example, in the intestine of Charadrius hiaticula 

 a small Trematode was found in great numbers, which ou 

 superficial examination might have been mistaken for a 

 Levinsenia sp., but on closer inspection displayed a cirrus 

 and a cirrus-pouch " *. I have no doubt that he had before 

 him members of the genus Maritreina, and in particular 

 M. gratiosum and M. humile. 



Equally interesting is the occurrence in Paludestrina 

 stagnalis of two cercariee, C. oocysta and C. pirtim, first 

 discovered and described by Miss Lebour t- These show 

 very close resemblance to species of the genus Maritrema. 

 C. oocysta shows well-marked testes, ovary, and cirrus-pouch, 

 and has thus reached a very advanced stage of development 

 for a ccrcaria. In many respects it agrees closely with 

 Maritrema humile, but the fact that the oral sucker is greater 

 than the ventral seems opposed to its identification as the 

 larval form of that species. Cercaria pirani has not attained 

 such a degree of development, there being no evidence of 

 •genital organs, but the configuration of the alimentary and 

 xcretory systems leaves little doubt that it is the larva of 

 pme Maritrema species. The anterior commissure of the 

 xcretory system differs only from my description of a similar 

 structure in M. gratiosum in being behind the pharynx in- 

 stead of in front. The suckers are practically equal, which 

 agrees with the condition in M. gratiosum, but the intestinal 

 diverticula are shorter. It is thus impossible at this stage 

 to identify the cercariaj with certainty, but there can be no 

 doubt that they belong to this or some closely allied genus. 



:)ii Genus Psilostomum, Looss. 



C 



Psilostomum brevicolle (Crepl.). 



1 liave found this species not only in the intestine and 

 caec: of Hcematopus ostralegus, but frequently also in the 

 intCNtme, cseca, and rectum of Oidemia fusca, and in the 

 intestine of O. nigra. Psilostomum oxyurum (Crepl.) has 



* Centralbl. f. Jiakter. xxvii. p. 739. 



+ Trans. Nat. Hist. Soc. Northumbeiland &c., new series, toI. i. pt. 3, 

 pp. 445 6. 



