MALACOPTERYGII 



S6S 



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.-^ 



The imperfectly known Cretaceous Crossognathidae (Crosso- 

 gnathus 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 1 3 ; stomach 



siphonal; pyloric appendages more or less numerous (17 to 



200). Breed in fresh water. Salmo, Bracliymystax, Stenoclus, 



Coregonus, Phylogephyra, Thymallus. 

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



pyloric appendages in moderate numbers (1 2 to 20). Argentina. 



^ 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. 



