1G4 On the Ifijhnd J>eliocen the Bream and the Ilad<L 



Bream. Hybrid. Riicld. 



riiaryugeal teeth 5 — 5 5 — 5 to 2 . 4 — 5 . 3 to 



2 . 5—5 .2 3 . 5—5 . 3 



Branched rays iu dorsal fin (8)9(10) (8)9(10) 8-9(10) 



„ „ anal „ 23-29 15-18 10-12 



Scales hi the lateral line 49-57 46-50 39-44 



„ between origin of dorsal fin 



and lateralline 11-14 9^-10^ 7-8 



,, between lateral line and base 



of pelvic fin 6-7 3^-5^ 3-4 



Vertebra3 43-45 "42^ 37-39 



Yarrell's skin and the specimens from Colebrooke and 

 Thetford had been determined as Abramis blicca (white bream 

 or bream-flat), a species of which the exact distribution in 

 ihe British Isles is not yet satisfactorily made out, but which 

 does not seem to occur in Ireland. The white bream is in 

 many respects intermediate between the rudd and the bream, 

 but differs from the hybrid above described iu the less oblique 

 mouth, larger eye, different pharyngeal dentition (teeth 

 usually 2 . 5 — 5 . 2), different number of fin-rays (dorsal with 

 8 branched rays, anal with 19 to 24), and higher position of 

 the lateral line (at g or more of the height of the body in the 

 middle of the length of the fish). The number of scales in the 

 lateral line (45 to 50) is practically the same, but in a trans- 

 verse series there are often fewer above and more below the 

 lateral line (g^g- instead of ^^f). 



The hybrid bream and rudd is also very similar to the 

 hybrid bream-flat and rudd, which differs from it in the same 

 way that the bream-flat does from the bream, i. e. in the 

 smaller size (maximum length 250 mm.), the larger scales 

 (40 to 46 in the lateral line, 8 or 9 between origin of 

 dorsal fin and lateral line, 4 or 5 between lateral line and 

 base of pelvic fin), fewer fin-rays (dorsal usually with 8, 

 anal with 12 to 17 branched rays), and more numerous 

 pharyngeal teeth (3.6—5.3 to 2.5—5.2). The mouth 

 is less oblique and extends further back, whilst the lower 

 caudal lobe is scarcely longer than the upper. The silvery 

 body, pale fins, and large eye also appear to hd characteristic. 

 This hybrid (Abrarnis blicca x Lcuciscus erythrophthalinus) 

 is represented by two specimens in the British Museum 

 (Giinth. Cat. Fish. vii. p. 233, 1868), and has been described 

 by a number of continental authors. Fatio's detailed account 

 (Faun. Vert. Suisse, iv. p. 376, 1882) and Sraitt's descrip- 

 tion, accompanied by an excellent figure (' Scandinavian 

 Fishes,' p. 807, fig. 200, 1895), may be specially mentioned. 



Although not uncommon on the Continent, this hybrid 



