48 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 Ichthyodectidcz (Saurodontidce) . Of these, Portheus, Ichthyodec- 

 tes, Saurocephalus (Saurodon), and Gillicus 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 Ctenothrissidae. A related family, Ctenothrissida, is 

 represented solely by extinct Cretaceous species. In this group 



FIG. 37. Ctenothrissa vexillifera Pictet, restored. 



(After Woodward.) 



Mt. Lebanon Cretaceous. 



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 PhractolamidcB the interopercle, according to 

 Boulenger, is enormously developed. 



The Notopteridae. The Notopteridcs 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 



