HOLOCEPHALI. 109 



developed, placed low. Ventral fins abdominal. Males with 

 claspers attached to ventrals. Skin scaleless, its muciferous sys- 

 tem well developed. 



This group generally includes six families. 



Order CHIMAEROIDEI. 



Characters included in those of the sub-class. 



Family CHIM^RID^E. 

 THE CHIMERAS. 



Body elongate, rather robust anteriorly, tapering posteriorly. 

 Head compressed. Mouth inferior, small. Upper lip deeply 

 notched. Jaws with teeth confluent into four bony plates above 

 and two below. Nostrils confluent with mouth, separated by nar- 

 row isthmus. Free gills 3, half gills 2, one on each side. Rakers 

 small. Isthmus moderate. Males usually with cartilaginous hook 

 on snout above, prickly at tip. turned forward. No spiracles. 

 Skin naked, rarely somewhat prickly. Lateral line present, usually 

 branched anteriorly. Dorsal usually divided, anteriorly with 

 strong posteriorly grooved spine. Caudal low, fold-like. Pec- 

 torals free, low. Ventral abdominal, many rayed. Males with 

 claspers. 



The existing forms are remarkable for their striking appear- 

 ance. They are all natives of deep water and cold seas. Repro- 

 duction is oviparous, the egg-cases long, elliptical and with silky 

 filaments.- About 17 genera have been described, all extinct, and 

 only C Mincer a persisting to the present time. Possibly CMmcera 

 affinis (Capello) may occur in deep water off our coast, though 

 it has not ever been so recorded. 



Passalodon was founded on vomerine teeth and Psittaoodon 

 on mandibular teeth of two European fossils. Woodward says 1 

 "the species mentioned below have also been determined upon 



'Cat. Foss. F. Brit. Mus., II, 1891, p. 84. 



