THE BOW-FIN. 
5° 9 
northern lakes, but remains of extinct species have been obtained, not only from 
the Eocene rocks of the same country, but likewise from the upper Eocene and 
Miocene strata of Europe. Carnivorous in its diet, preying both upon other tish 
and also upon aquatic crustaceans and insects, the bow-fin is capable of living for 
fully an hour out of water ; and when in its native haunts, especially where the 
water is foul, comes frequently to the surface to breathe, rising to the surface, and 
taking in large mouthfuls of air without the emission of a single bubble. When 
near the surface, this fish often utters a bell-like note, probably due to the passage 
of air from the air-bladder. The breeding-season, during which the colours of the 
fish are more brilliant, lasts from May till the beginning of June. The bow-fins 
breed among floating islands of herbage fringing the great lakes. Here they lay 
thousands of minute eggs on the water-plants which form the base of a series of 
tunnels, composed partly of root-fibres, and partly of a moss-like growth. Of the 
nest thus formed, the male fish takes entire charge till the fry are hatched; the 
development of the eggs being unusually rapid. The embryos, while agreeing in 
many respects with those of the typical ganoids, are stated to approximate in other 
points to those of the higher bony fishes. Megalurus, from the upper Jurassic, is 
an allied extinct genus with a short dorsal fin and fulcra; while the Jurassic 
Eurycormus and Liodesmus likewise belong to the same family. 
Among several 
Extinct Families. . . „ 
extinct families of 
which the members are mostly 
of Jurassic age, we may notice 
the Pachycormidce, as represented 
typically by Pachycormus, in 
which, while the body and jaws 
have the same form and structure 
as in the bow-fish, the notochord 
is persistent, and the ethmoid bone fused with the vomer to form a long beak; the 
fin-rays being slender and closely set, the dorsal fin short, and fulcra absent or 
minute. Eugnathus and Caturus are well-known members of a third family 
distinguished by the vertebrae being usually represented by incomplete rings, by the 
large fulcra, and the short dorsal fin; the caudal 
fin being forked. The Pycnodonts, ranging from 
the Lias to the Eocene, constitute another family 
group, in which the body is either deeply fusiform 
or rhomboidal; the notochord has no ossification 
around it; the cleft of the mouth is narrow ; the 
teeth are small, nodular, and aggregated into a 
pavement, without vertical successors; the gill- 
cover is of a very simple type; branchiostegal 
rays and fulcra are alike absent; and the dorsal 
fin is elongated. The family is typically repre¬ 
sented by the genus Pycnodus ; but we have 
figured as an example of the dentition the lower 
EIGHT HALF OF THE LOWER JAW OF A ^ 1 ^ . „ ... 
pycnodont (Mesodon). — After Gaudry. j&W 01 tb.6 £11116(1 J\IcS0Cl07l . x 6t cinotllGl I&mily 
SKELETON OF AN EXTINCT AMIOID ( CdtUTUS ). 
