SEA-FISHERIES LABORATORY. 193 



adhesive disk is one of the characters by which species are 

 defined. In three species the disk is circular, and in a 

 fourth lingulate. Figure 4 shows the shape and position 

 of the adhesive disk in the specimen from Fishguard Bay. 

 This is the first time we have found the genus in the Irish 

 Sea. 



A number of bass [Labrax] and mackerel were 

 examined during 1905. The Trematodes already recorded 

 from these fish were again found. 



(5) Microcotyle labracis, van Ben. and Hesse. — Plate 

 IX., fig. 3, 



(6) and Diplectanum aequans, Diesing. — Plate IX., 

 fig. 4, are from the bass. The former is a large species, 

 but appears to be rare, while the latter, a very small form, 

 is always plentiful on the gills of the fish taken near 

 Piel. 



(7) Octobothrium alosae, Hermann. — Plate IX., fig. 1. 

 A large number of specimens were found on the gills 



of a shad, Clwpea alosae, sent to us by Mr. Hobert Jones, 

 Fishery Officer at Carnarvon. Not previously recorded 

 for the district. 



(8) Octobothrium scombri (Kuhn) — Plate IX., fig. 2, is 

 the mackerel trematode. This is a very slender species 

 and easily overlooked. 



Two members of the Hirfdinea were added to our 

 list during 1905. 



(9) Trachelobdella lophii (van Ben. and Hesse), from 

 the gill chamber of an angler fish (Lo'phius piscatorius) 

 brought to the Piel laboratory by the steamer. 



(10) Platybdella soleae (van Ben. and Hesse). 



This is the little brown thread-like body often seen on 

 the black side of the common sole. A number of the soles 

 caught between Lancashire and the Isle of Man in 1905 

 were covered with the Platybdella* 



o 



