90 :\Ir. W. Xicoll on the 



distiuguisbed, and there wore no ova (so that the specimen 

 was probably immature). Together with tlie size of the 

 body and the condition of the suckers these characters seem 

 sufficient to establish identity with Distomuin nioUissimum as 

 described by Leviu'^en *. 



Genus Derogenes, Liihe. 



Derogenes various, Miiller. 



This has proved one of the most widely distributed Trema- 

 todes in this locality, and has occurred in the following 

 hosts: — Gadiis merlangus (intestine), FIippor/los.<tu.<} vulgaris 

 (stomach), Rhombus ina.vinuis (oral cavity, oesophagus, and 

 stomach), Rho)nbus Icevis (stomach), Pleuronectes liinanda 

 (oral cavity, oesophagus, and stomach), and Cottus scorpius 

 (intestine). It is here recorded for the first time from 

 Rhombus ma.i-imus and Plcuronectes limanda, and in these it 

 has occurred most frecpicntly. 



Its characters are so well known tliat it calls for no descrip- 

 tion here. The limits of size are wide, Stossich giving them 

 as l'd-7 mm. I have found adult specimens less than I mm. 

 bmg, and the largest example obtained was 3"4 mm. long 

 from the stomach of the turhot. The most common size is 

 l"5-20 mm. The oral sucker in individuals of that size has 

 a diameter of •19-"24 mm., and the ventral sucker •33-'40 mm. 

 The ova vary greatly in specimens from different hosts. The 

 limits in length are •050-"062 mm.^ and in breadth "025- 

 "034 mm. Those in front of the ventral sucker are always 

 larger than those behind, and it is in the latter that the 

 greatest variations are to be observed. Thus in an example 

 from the halibut the ova in the anterior part of the body 

 measured '059 X "032 mm., in the posterior part '057 X "027 

 mm. The approximate size of the ova just about to be 

 extruded may be taken as 'OSS-'OGO x 'OSl-OJi mm. 



Derogenes cacozelus, sp. n. (PI. III. fig. 10.) 



Found in the intestine and vectnxa o{ Hippoglossus vulgaris 

 and the intestine of Pleuronectes limanda. It is not at all 

 common, only a few specimens having been obtained. It 

 bears a close resemblance to Derogenes various, Miiller, but 

 the large vesicula seminalis and the small ova differentiate it 

 at once from that species. 



The body is elongated, cylindrical, broadest in the middle, 



* Oversigt Kgl. Dansk. Selskab. 1881, pp. 59-Gl, pi. ii. fig. 4. 



i 



