476 WILLIAM NICOLL. 



that the ventral sucker is somewhat larger and more globular than in the 

 Clyde specimens. It is thus not a feature to distinguish this species from 

 P. genu. 



Peracreadium genu (Uud.). 



Nicoll, 1910, pp. 326-8. 

 This was obtained twice from the intestine of Labrus herggylta, but 

 never from any of the other Lahridae (over 30 were examined). A 

 single immature specimen, however, occurred in the intestine of a shanny 

 {Blennius pholis). It was only 4 mm. long. The testes were oblique, 

 and the ovary on the right side of the anterior testis. The cirrus-pouch 

 reached almost to the ovary. The yolk glands were not visible, and there 

 were no ova. It seemed impossible to determine whether this specimen 

 should be regarded as P. genu or P. cofntnune, but in any case it must 

 be regarded as an adventitious parasite of the shanny. 



Genus CAINOCREADIUM Nicoll. 

 Cainocreadmm labracis (Dnjardin). 

 Johnstone, 1908, pp. 44-53. 

 Half a dozen specimens of this species were taken from the intestine 

 of the only bass {Lahrax Iwpus) examined. 



Genus HELICOMETRA Odhner. 

 Helicometra pulchella (Paid.). 



This was by far the commonest member of the AUocreadiidae met with. 

 As a parasite of httoral fishes it largely replaces Podocotyle atomon, which 

 is predominant on the east coast. At Plymouth it was met with in 

 twelve different hosts : Serranus cabrilla, Trigla pint, Gohius paganellus, 

 Blennius pJiolis, Blennius gattorugine, Lepadogasfer gouanii, Labrus mixtus, 

 Labrus berggylta, Ctenolabrus rupestris, Zeugopterus punctatus, Anguilla 

 vulgarus and Conger conger. Ninety specimens of these fishes were ex- 

 amined, and the parasite was met with thirty-three times (i.e. 3 in 8). Its 

 chief hosts are the goby and the blennies. In these it occurred three 

 times in five. 



A fairly full description, partly based on the material collected at 

 Plymouth, has already been given (Nicoll, 1910, pp. 335-40). The dis- 

 tribution of this species is rather noteworthy. It has been recorded from 

 the Mediterranean, from the English Channel and from the v est coast 

 of Scotland. It has never been recorded from the North Sea. 



H. pulchella (Rud.) of Odhner (1902) from Northern fishes, is probably 

 a distinct species. 



