274 Isospondyli 
in which region Chirocentrus polyodon occurs as a fossil. Numer- 
ous fossil genera related to Chirocentrus are enumerated by 
Woodward, most of them to be referred to the related family 
of Ichthyodectide (Saurodontide). Of these, Portheus, Ichthyodec- 
tes, Saurocephalus (Saurodon), and Guillicus are represented by 
numerous species, some of them fishes of immense size and great 
voracity. Portheus molossus, found in the Cretaceous of Nebraska, 
is remarkable for its very strong teeth. Species of other genera 
are represented by numerous species in the Cretaceous of both 
the Rocky Mountain region and of Europe. 
The Ctenothrisside—A related family, Ctenothrisside, is 
represented solely by extinct Cretaceous species. In this group 
ON 
Fic. 208.—Ctenothrissa vexillifera Pictet, restored. Mt. Lebanon Cretaceous. 
(After Woodward.) 
the body is robust with large scales, ctenoid in Ctenothrissa, 
cycloid in Aulolepis. The fins are large, the belly not serrated, 
and the teeth feeble. Ctenothrissa vexillifera is from Mount 
Lebanon. Other species occur in the European chalk. In the 
small family of Phractolemide the interopercle, according to 
Boulenger, is enormously developed. 
The Notopteride.—The Notopteride is another small family 
in the rivers of Africa and the East Indies. The body ends in 
a long and tapering fin, and, as usual in fishes which swim by 
