XVIII HOLOSTEI 5OI 
process may be completed within from 4 to 8 days. When 
hatched the larvae are about 5 to 6 mm. long. They possess a 
large yolk sac and a preoral sucker for attachment. The pectoral 
fins are conspicuous structures before there is any trace of the 
pelvic fins. 
- ~\) 
WM wee Zr 
Fig. 296.—Amia and its nest. (From Bashford Dean.) 
The Amiidae, represented by Megalurus,' first appear in the 
Upper Jurassic of Dorset, France, and Bavaria. In the Creta- 
ceous period the family is represented by Amzopsis. Species of 
Amia occur in the Eocene of Europe and North America. In 
the former area the genus became extinct at the close of the 
Lower Miocene period, but in the latter Amia calva still 
survives. . 
Fam. 6. Pachycormidae.— Large-mouthed, predaceous Amioid 
Fishes with a more or less prominent snout and a short dorsal 
fin. Scales rhombic but thin, rounded behind, and overlapping, 
sometimes absent. <A single large jugular plate. 
In the earlier forms (e.g. Pachycormus, Lias) the snout is but 
slightly produced, but in Hypsocormus (Upper Jurassic), and 
1 This genus also occurs in the Cretaceous of Brazil (Smith Woodward, 
A.M.N.H. (7) ix. 1902, p. 87. 
