7iew and little-known Trematodes. 523 



Viuioiis slructmcs are j)io|)oitioiiately large. Comparison 

 with Jiigerskiokl's specimens will best be seen by tlie 

 following list of measurements : — 



Jiigeiskiuld. 



mm. mm. 



Ltntrth •4w» --(30 So -1-30 



Maximum breadth -20 --22 -35 - -44 



Oral sucker (diauieter) •048--060 -07 - -08 



Ventral sucker (diameter) •0r)2--0G4 -07 - -095 



rbaryux (length) •0:i:3--036 -043- -049 



„ (breadth) •020-022 -OSO- -037 



Undivided intestine -10 -20 -37 - -61 



Intestinal diverticula -1 -13 -23 - -37 



Ovary -030 -09 - -11 



Testes 13 x '09 



022- 025 X 



'''■- -O^SX-OU ..oo9_.oii 



From tliis it is evident that the only point of correspondence 

 is in the size of the ova. In this connexion some of my 

 specimens show a number of ova towards the end of the 

 utoru.^, which are much larger than the others, measuring 

 •028 X '019 mm. A feature which Jiigerskiold does not 

 mention is that the uterus starting on the right side con- 

 tains almost colourless ova on that side, while on the left the 

 ova have a brownish-yellow colour and are very slightly 

 larger. 



As regards the general contour, Levinsen figures Distomum 

 pygmcEuin somewhat after the fasliion of an isosceles triangle. 

 Jiigerskiold, however, never found specimens of that shape 

 either in Lams or in Sotnateria. To his mind the form is 

 biscuit-shaped (" biscuit-lijrmig ") and sometimes, but rarely, 

 club-shajjed (" keulen-forinig "). He depicts * a young speci- 

 men from Jlccmatopus ostralegus which shows this latter 

 shape, lie add.s that in life the animal is probably pear- 

 shaj)ed, with a greater or less concavity on tlie ventral side 

 of tlie anterior part of the body. Now the majority of the 

 examples which have come under my observation liavo, or 

 tend to have, this pear-shaped or club-shaj)ed form, although 

 at the same time they are considerably flattened dorso- 

 ventrally ; many of them are, certainly, not so atteimated 

 anteriorly, but there is always a marked distinction, often, 

 indeed, a constriction between anterior and i)Osterior parts, 

 and the latter is always well rounded. 



Jagerskitild makes no mention of having found Levinsenia 

 similis in the intestinal caeca of Larus arjentatus. 1 found 



* Op. cit. p. 734. 



