CHISMOPNEA. 9 



description and figure. It anticipated Dicerobatus Blainville, 1816. 

 Cephalopterus Risso, 1810, had been preoccupied. Aodon of Lacep^de, 

 1798, was founded on toothless sharks Squalus massasa and S. kumal men- 

 tioned by Forskael, 1775, and a toothless head described by Brunnich, 1768. 

 The name is not appropriate; the species are unrecognizable, though there 

 is a possibility that Squalus edentulus Brunn., renamed Aodon cornu by 

 Lacepede, may have been the head of a species of Mobula or of Manta. 



SYSTEMATIC DESCRIPTIONS. 



Chondropterygia. 



This class contains fish-like vertebrates with a skeleton that is more or less 

 completely cartilaginous, with six to eight branchial arches, with fins having 

 cartilaginous basal supports and fibrous extensions, with teeth not implanted in 

 the jaws, with spiral folds in the intestine, and with internal fertilization of the 

 eggs. There is no air bladder; the males have paired intromittent organs; and 

 the embryos have deciduous external gills. 



Two orders may be separated as follows : — 



An erectile dorsal spine; vertebrae undifferentiated 



one external gill opening; teeth few, plate-like . . . Chismopnea 

 No erectile dorsal spine; vertebrae more or less differentiated 



five or more gill openings; teeth numerous . . . Plagiostomia 



CHISMOPNEA. 



Body elongate, tapering to a point in the tail; erectile spine of the dorsal 

 above the shoulders; pectorals free. Mouth inferior; upper jaws fused with 

 the skull, lower directly articulated to it; four upper and two lower teeth. 

 Hemispheres of the brain distant from the optic lobes. Eggs incased in a 

 fibrous horny shell; embryo hatched after extrusion of the egg. Male witli a 

 frontal tenaculum, with ventral tenacula and with claspers. 



For a systematic account of this order see Garman, 1911, Memoirs M. C. Z., 

 40, p. 79-102. The three families recognized may be distinguished thus: — 



Notochord with narrow rings 



snout not produced, short Chimaeridae 



snout produced in a long pointed rostrum . . Rhinochimaeridae 



Notochord without narrow rings 



snout produced in a leaf-like appendage .... Callorhynchidae 



