PISCES. 205 
Orper VII. Loprnoprancutt. 
Internal skeleton only partly ossified. Scales ganoid. Gills tufted, gill- 
opening small. Swimming bladder without air-duct. 
Hippocampide. Syngnathide. 
Orper VIII. Ganorpet. 
Internal skeleton bony or cartilaginous. Scales ganoid. First fin-ray 
usually a spine. Swimming bladder with an air-duct. 
Sauride. Sturionide. Cephalaspide. 
Pycnodontide. Acanthodei. 
Lepidoidei. Dipteride. 
Orper IX. ProropTert. 
Internal skeleton partly bony, partly cartilaginous. Scales cycloid. 
Pectorals and ventrals as flexible filaments. Gills filamentary, free. No 
pancreas. Swimming bladder as a double lung, with an air-duct. Intestine 
with a spinal valve. 
Sirenoidei. 
Orper X. Ho.nocepHatt. 
Internal skeleton cartilaginous. External skeleton as placoid grains. 
Most of the fins with a spinous first ray ; ventrals behind the pectorals. 
Gills laminated, attached by their margins; a single external aperture. 
No swimming bladder. Intestine with a spiral valve. Copulation between 
the sexes. 
Chimeeroidei. Edaphontide. 
Orper XI. Puaciostomt. 
Internal skeleton cartilaginous, or partly ossified. External skeleton 
placoid. Gills fixed; with five or more gill-openings. Swimming bladder 
none. Scapular arch not attached to head. Ventrals behind the pec- 
torals. Intestine with spiral valve. 
Hybodontide. Lamnide. Rhinobatide. 
Cestraciontide. Alopeciide. Torpedinide. 
Notodanide. Scymniide. Raiide. 
Spinacide. Squatine. Trygonide. 
Scyllide. Zygenide. Myliobatide. 
Nictitantes. Pristide. Cephalopteride. 
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