Trematode Parasites of British Birds. 257 



possess no sectional preparations tliis evidence is not con- 

 clusive. The ventral sucker in Tccotrema concavvm a])pe;irs 

 to be in a more degenerate condition tlian in T. luigua. 

 Moreover, the voluminous vesicnla seminalis of the latter is 

 very much reduced in the former. A less important differ- 

 ence is the symmetrical arrangement of the testes in Toco- 

 trema concavum in contrast to the oblique arrangement in 

 T. lintjua. 



The occurrence here of a new species agreeing very closely 

 with Tvcotrema lingua accentiiates the difference between 

 the latter and Distomum concavum. Moreover^ considering 

 the large number of hosts from which Distomum concavum 

 has been recorded, it is quite possible that two or more 

 closely similar species may have been confused. The form 

 which I have obtained from Phalacrocorax graculus is almost 

 identical with Distomum concavum, but it ditlers from 

 Miihling^s description in one or two important features, 

 which may cause it to be regarded as distinct. Distomum 

 Mvehlingi shows considerable resemblance to Tocotrcma lingua, 

 and if it should prove to have a genital sucker, as opposed to 

 Miihling's description, it would be classed in the same grouj). 

 For these reasons I am inclined to regard Distomum concavum 

 as the type of a genus distinct from, but closely related to, 

 Tocotmna. To this genus Liihe's name Cryptocotyle, 

 hitherto regarded as a synonym of Tocotrema, might con- 

 veniently be applied. Liihe took Distomum concavum as 

 type, while the genus Tocotrema is founded on Distomum 

 lingua as type. 



7 ocotrema jejunum, sp. n. 



This species occurred fairly frequently in Totanuft calidris. 

 It is of somewhat smaller size than T. lingua, the length 

 varying from •87-l*77 mm., but the normal length is 

 probably not beyond 1'3 mm. It displays_, however, an 

 extraordinary amount of extensibility. Almost every ex- 

 ample was well extended, and in a large number the extension 

 was so great that the}' had almost the appearance of threads, 

 the body being often bent and twisted in a grotesque fashion. 

 As might be expected, the maximum breadth occurring in 

 the posterior part of the body is not at all constant, varying 

 from ^ to I of the body-length. The normal figure is 

 probably about ^, being found in examples of I'O mm. to 

 i-.2 mm, long. The shape is not like that cf T. lingua, the 

 anterior part of the body being more tapering and the 

 posterior part more rounded. In a normal specimen (I'O- 

 12 mm.) the oral sucker measures '015 mm. The ventral 



