24i Dr. W. Nlcoll and Mr. W. Small on 



of the term is evidenced by the fact that althougli the 

 aperture is sharply enough defined, the sucker itself does not 

 have the well-marked outline usually associated with the 

 ventral sucker. Furthermore, the vestigial ventral sucker 

 can be made out a little in front of the genital aperture, but 

 its apeiture is concealed in the genital sucker. Traces of two 

 small testes can be detected in front of the ends of the 

 intestinal diverticula, but none of the other organs are visible. 

 The cuticle, as in the adult, is set with numerous regular 

 sc^le-like spines. 



This larval form appears to have hitherto escaped obser- 

 vation. Its identification as the cercaria of Crj/ptocotyle 

 concava (Crepl.) seems quite justitiable "without further proof, 

 for it possesses the characters of that species in a marked 

 degree and there is no other British species with which it is 

 likely to be confused. We have found, too, that Phalacro- 

 corax qraculus (the shag), which is one of the hosts of the 

 adult parasite (so far, the only British host), feeds largely on 

 small plaice, dabs, and flounders. 



Stephanochasmus haccatus, Nicoll. (Cercaria.) 



AVe have to record this larva from Pleuronectes limandn. 

 Only one cyst was obtained, but no special search was made 

 for n.ore; its frequent occurrence in young Pleuronectids has 

 already been fairly well established. The cyst was embedded 

 under the skin and its wall was very thin and membranous, 

 the thick outer covering, mentioned by Miss Lebour *, having 

 juobabiy been removed in freeing the cyst from the tissues 

 of its host. Its diameter was about '7 mm., but it was 

 more or less ovoid, according to the movements of the en- 

 closed cercaria. 



The length of the cercaria is l'8-2'0 mm. and in structure 

 it agrees very well with the adult Stephanochasmus haccatus. 

 Anteiiorly it is covered with numerous regularly arranged 

 spines, which disappear a short distance behind the ventral 

 sucker. The oral sucker is encircled by two rows of larger 

 and stouter spines which are closely applied to tlie aperture. 

 They number 28 in eacli row and are regularly and sym- 

 metiically arranged, no gap being lett in either of the rows. 

 Those of the anterior row measure "OSG mm. in length, in 

 the posterior row •04 mm. on an average. There is slight 

 variation in length. 



The oral sucker is terminal and measures '186 mm. in 

 diameter; the ventral sucker lies near the middle of the 



* 0/;. cit. p. 14. 



