xxi MALACOPTERYGII 565 



ranean, but it is also regularly fished in Holland, especially in 

 the Zuydersee, where it breeds, as well as in the Mediterranean ; 

 it makes only temporary appearances, and has not been observed 

 to spawn, in the English Channel, although eggs have recently 

 been obtained off the coast of North Lancashire. 1 



The imperfectly known Cretaceous Crossognathidae (Crosso- 

 gnatlius and Scyllaemus), referred by some authors to the Percesoces, 

 should probably be placed with or near the Clupeidae. 



Fam. 17. Salmonidae. Margin of the upper jaw formed by 

 the praemaxillaries and the maxillaries. Supraoccipital in contact 

 with the frontals, but frequently overlapped by the parietals, 

 which may meet in a sagittal suture ; opercular bones all well 

 developed. Basis cranii double. Eibs sessile, parapophyses very 

 short or absent ; epineurals, sometimes also epipleurals, present. 

 Post-temporal forked, the upper branch attached to the epiotic, 

 the lower to the opisthotic ; postclavicle, as usual, applied to 

 inner side of clavicle. A small adipose dorsal fin. Air-bladder 

 usually present, large. Oviducts rudimentary or absent, the ova 

 falling into the cavity of the abdomen before exclusion. 



Marine and fresh-water Fishes, mostly from the temperate and 

 Arctic zones of the northern hemisphere : one genus (Retropinna) 

 on the coasts and in the rivers of New Zealand ; a few deep-sea 

 forms (Argentina, Microstoma, Nansenia, Bathylagus) occur in 

 the Arctic Ocean, the North Atlantic Ocean, the Mediterranean, 

 and the Antarctic Ocean, down to 2000 fathoms. Apparently 

 of comparatively recent age, no remains older than Miocene 

 (Osmerus, Thaumaturus, Prothymallus) being certainly referable 

 to this family. The recent genera may be grouped as follows : 



A. Air-bladder present. 

 a. Branchiostegal rays 8 to 20; ventral rays 9 to 13; stomach 



siphonal ; pyloric appendages more or less numerous (17 to 



200). Breed in fresh water. Salmo, Brachymystax, Stenodus, 



Coregonus, Phylogephyra, Thymallus. 

 1. Branchiostegal rays 6 ; ventral rays 11 to 14 ; stomach caecal ; 



pyloric appendages in moderate numbers ( 1 2 to 2 ). Argentina. 



1 On the life-histories of the British Clupeids, cf. Heincke, " Naturgeschichte des 

 Herings" (Abh. Deutsch. Seefisch. Ver. ii. 1898) ; J. T. Cunningham, " Life-History 

 of the Pilchard " (J. Mar. Biol. Ass. [2] iii. 1894, p. 148), and the manuals of the 

 latter author (Marketable Fishes of Great Britain, 1896) and of M'Intosh and 

 Masterman (British Marine Food-Fishes, 1897). 



On the accessory branchial organs of some genera, see p. 294. 



