||N0.i32i. ELASMOBRANCHIAT^ FISHES— JORDAN AND FOWLER. 667 



Subclass HOLOCEF»HALI. 



, CHIMERAS. 



! Skeleton cartilag-inous. Gill cavity with four clefts vvitiiiii, but liav- 

 iing one external opening only, which is covered by a fold of skin. 

 No spiracles. Mouth inferior. Jaws Avith teeth, confluent into bony 

 r plates; upper jaw, palate, and hyoniandilnilar, coalescent with the skull; 

 intestine with a spiral valve. Pectoral fins normally developed, placed 

 • low; ventral tins abdominal, with claspers in the male; a cartilaginous 

 j hook, with a l)rush of teeth at the tip (frontal holder) on the forehead 

 I of the adult male. Derivative radii sessile on the sides of the basal 

 i bones of the limbs. Skin scaleless, its muciferous system well devel- 

 oped. This group contains a single order, Chinueroidei, among exist- 

 ing fishes; many extinct forms belong to it, and the group is perhaps 

 . not less ancient than that of the sharks. 

 {oXog.^ solid; Ke(/j(x\t}, head.) < 



Order V. CHIM^^ROIDEI. 



CHIMiEROIDS. 



Characters of the order, included above. The grouj) includes three 

 existing families, Rhinochima?rida? (Bassalian), Chimwridse. and C'allo- 

 rhynchida^ (Antarctic). The two families found in Japan are thus 

 defined b}' Mr. Garman: 



a. Proboscis long and pointed; lateral canal system subtu])ular; notochord with 

 rings; cerebral hemispheres distant from both olfactory and optic lobes. 



Rhinochim.erid-e, XXIII. 

 aa. Proboscis absent; lateral canal system, silicate; notochord with ring-like seg- 

 ments; cerebral hemispheres fused with the olfactory lobes, and distant from 

 the optic lobes Chim.erid.e, XXIV. 



Family XXIII. RHINOCHIM^ERID.E. 



Snout ver}- long, with a cartilaginous midrib, and foliaceous lateral 

 expansions of the skin at the base. Two dorsal fins, the anterior one 

 with an immense triangidar spine, finely serrated on its lateral edges. 

 Tail ver}^ elongate, with filamentous tip. Frontal region in the adult 

 male with a ''frontal holder," as in Chiman-a. Ventral claspers small 

 and simple, gill-openings separated by a wide isthmus. Lateral canal 

 system subtubular; notochord with rings; cerebral hemispheres dis- 

 tant from ])oth olfactory and optic lobes. Two genera — Harrlotta 

 in the deep waters below the Gulf Stream, and RJihKxhhiia'ra in 

 similar situations in Japan. ILirriotfd has t(H^th much like those 

 of Ch>tii;fi'<i. liJuiKK'Jiunsera is the most primitive of existing 

 Chimnn'oids. 



