Trematode Parasites of British Birds. 2i)9 



In connection with the above described three species it is 

 interesting to read Jiigerskiold's note, in which he says : — 

 " During my search for Levinsenia 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 com])clled to assign them to other geuera. 

 Thus, for example, in the intestine of Churadrius hiuticula 

 a small Trematode was found in great numbers, which on 

 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 Maritrema, and in particular 

 M. yratiosum and M. humile. 



Equally interesting is the occurrence in Paludestrina 

 stagnalis of two cercarite, C. oocysta and C. pirum, first 

 discovered and described by Miss Lebour f. 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 cercaria. 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 pirum has not attained 

 such a degree of development, there being no evidence of 

 genital organs, but the configuration of the alimentary and 

 excretory systems leaves little doubt that it is the larva of 

 some Maritrema species. The anterior commissure of the 

 excretory 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. yratiosum, but the intestinal 

 diverticula are shorter. It is thus impossible at this stage 

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

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



Genus Psilostomum, Looss. 



Psilostomum brevicolle (Crepl.). 



I have found this species not only in the intestine and 

 cseca of Hamatopus ostralegus, but frequently also in the 

 intestine, cieca, and rectum of Oidemia fusca, and in the 

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



• Centralbl. 1". iiakter. xxvii. p. 739. 



t Trans. Nal. Hist. iSoc. Nortiiumbeiland ilv;c., new series, vol. i. pt. 3, 

 pp. 44o H. 



