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.! 
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. Ribs 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, Thawmaturus, 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. 
b. Branchiostegal rays 6; ventral rays 11 to 14; stomach caecal ; 
pyloric appendages in moderate numbers (12 to 20). 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. 
