38 TREMATOtoES OF* THE NORTHUMBERLAND COAST 



Here I may record another larval Trematode from the small 

 bivalve Scj-obicnlaria tenuis from Fenham Flats. This mollusk 

 was found by Villot to harbour several larval Trematodes. 

 One of these (viz., Echinosionium leptosoi?iuin) has already 

 been described* in a former paper. I am now able to record 

 another of Villot's species, namely, Cercaria fissicauda, which 

 as Pelseneer points outf should be named Cercaria dichotoma, 

 Miiller. The sporocysts occurred in the liver, which was full 

 of them ; and in the same specimens the encysted cercarias of 

 Echinostomuin leptosomiivi were found in the foot. Pelseneer 

 found his specimens of C. dichotoma in Tellina solidula 

 (= Macoma balthicd). 



Cercaria dichotoma, Miiller (Plate II. fig. i, 2) occurs in 

 long knobbed sporocysts, very transparent and structureless, 

 in which many cercariae are crowded together. The cercaria 

 is about 0-20 mm. long, including the tail, which is slightly 

 shorter than the body, and forked. Anterior sucker 0*033 ^"i* 

 across, leading directly into a pharynx. Although Villot did 

 not see this pharynx, and described and figured the worm as 

 having none, yet it was seen by later observers and is very 

 distinct, measunng o'oi6 mm. in length. There is a long 

 cesophagus branching beyond the centre of the body into two 

 short lobes. The ventral sucker lies well behind the centre of 

 the body and measures 0*029 "^™- '^ diameter. An 

 elaborately curved horseshoe-shaped (or perhaps more strictly 

 lyre-shaped) excretory vesicle occupies most of the posterior 

 part of the body, and is continued along the tail and into 

 each fork of it. The granules contained in the vesicle are 

 the most conspicuous features of the cercariae within the 

 sporocysts. 



At present nothing seems to be -known about further stages 

 of this Trematode, and it is difficult to suggest to what genus 

 it may belong. I only found it once in about 50 specimens 

 examined. This cercaria was met with by Mr. Andrew Scott 



* Op. cit., Trans. Nat. Hist. Soc. Northbd., etc., p. 447. 



t Pelseneer, P., Op. cit., p 173. • 



