452 
ACTINOPTERYGII. 
varied as those of the existing Isospondyloiis family Mormyridse. ^ 
The more elongated and degenerate types are those inhabiting great 
depths. 
All the known fossil Scombridae occur in marine deposits. 
Synopsis of Extinct Genera and Genera representedj hy 
Extinct Species. 
I. Trunk fusiform. 
A. Two dorsal fins close together. 
Posterior dorsal and anal fins much ex¬ 
tended, perhaps without finlets . . Isurichthys (p. 453), 
Posterior dorsal and anal fins short and 
deep, with 8 to 12 finlets. Thynnus (p. 454). 
[Skull resembling that of Thynnus^ 
but deeper in proportion to its 
width. Eothynmis (p. 457).] 
B. Two dorsal fins well separated. 
Teeth very small and conical; about 30 
vertebrae; caudal pedicle without 
lateral keel; paired fins small; no 
enlarged pectoral scales . Scomber (p. 459). 
As Scomber, but with nearly 40 verte- ^ 
brae and larger pectoral fins .... Ealimphyes (p. 460), 
[Skull resembling that of Scomber, but 
with larger teeth . Scombrinus 
As Scomber, but caudal pedicle with 
lateral keel and pectoral scales 
enlarged. Auxis (p. 463). 
Marginal teeth large and laterally com¬ 
pressed, in single series; caudal 
pedicle with cartilaginous lateral 
keel . Cybium (p. 465). 
[Skull resembling that of Cybium, but 
shorter and without median fron¬ 
tal crest .. Eoccelopoma (p. 470).] 
[Jaws as in Cybium, but teeth round or 
ovoid in section . Sphyrcenodus (p. 473).] 
[Jaws as in Sphyrcenodus, but small 
teeth on dentary outside series of 
large teeth. Scombramphodon 
II. Tnmk much elongated. (p. 474).] 
Paired fins small ; finlets behind dorsal 
and anal fins . Thyrsitocephalus 
Pelvic fins rudimentary; dorsal fins (p. 476), 
continuous j no dorsal or anal 
finlets. Lepidopus (p. 477). 
^ G. A. Boulenger, Proc. Zool. Soc. 1898 (1899), p. 780. 
