176 OUTLINES OF ICHTHYOLOGY. 



tutes the upper jaw in other words, the jaw-bones being sol- 

 dered together. 

 Two Families. 



The CARTILAGINOUS FISH, or CHON- 

 DROPTERYGII (from the Greek chondros, 

 cartilage, and pterygion, a fin), consisting of two 

 Orders, viz. : 



ORDER I. 



CHONDROPTERYGII BRANCHIIS LIBERIS, or Cartilaginous Fish 

 with free gills. (From Latin bmnchice, gills, and liber, free.) 

 The Fish forming this Order have a single wide opening in their 

 gills, and a gill-cover as in the Bony Fish ; but no gill-rays. 



The Order contains two Families. 



ORDER II. 



CHONDROPTERYGII BRANCHIIS FIXIS, or Cartilaginous Fish 

 with fixed gills. (From the Latin branchice, gills, and fixis, 

 fixed.) These fish have their gills fixed at the outer edges, with 

 a separate opening through which the water from each gill 

 escapes. They have also small cartilaginous arches suspended 

 in the muscles opposite the gills, which may be called gill-ribs. 



They form two Families. 



The foregoing eight Orders are again subdivided 

 into Families, Genera, and Species, as already 

 stated. 



The following List exhibits in a tabular form 

 the classification above explained, with the addi- 

 tion of the names of the various Families : 



