24. CniM^RlD^. 53 



margins of the disk darker. {Dumeril.) Tropical waters of A.merica; 

 north to i^orth Carolina and San Diego. Eeaches a width of about 20 

 feet. 



C^Eaia hirosiris Wiilbaum " : Ccphaloptera vampi/ruH Mitcliill, Ann. Lye. Nat. Hist. N. 

 Y. 18:;,'3, 28: DiaboUchthyseUiotU Holnu's, Proc. Elliott Soc. Nat. Hist. 1856, ^^9 : Ceratop- 

 tera vampyrus Dumtlril, Hist. Nat. Poiss. i, GGO : Ceratoptem vampyrus Giiutlier, viii, 498.) 



Subclass HOLOCEPHALI. 



{The Chimccras.) 

 The characters of the single order. 



Okdee f.-holocephali. 



{The Chimceras.) 



Skeleton cartilaginous. Gill-cavity with four clefts within, but having 

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

 which is a rudimentary cartilaginous operculum. No spiracles. Mouth, 

 inferior. Jaws without separate teeth, but armed with bony plates. 

 Intestines with a spiral valve. No air-bladder. Jaws and palate 

 coalescent with the skull. Derivative radii sessile on the sides of the 

 basal bones of the limbs, separated from the articulation. Pectoral fins 

 normally developed, placed low. Yentral fins abdominal. Tail taper- 

 ing. Skin smooth or nearly so ; its muciferous system well developed. 

 A single family. 



(iZoZocej.>/jaia Giiutlier, viii, 348-352; iiAof, solid; «f0a/,//, head.) 



Family XXIV.— CHIM^RIDtE. 



{The Chimceras.) 



Body elongate, rather robust anteriorly, tapering posteriorly. Head 

 compressed. Mouth inferior. Cjiper lip deeply notched. Nostrils 

 confluent with the mouth, separated by a narrow isthiuus. Jaws with 

 the teeth confluent into four bony laminae above and two below. No 

 spiracles. ]\Iales with a i)ecu^^liar cartilaginous hook, armed with prickles 

 at the tip, and turned forward on the uppin* ])art of the snout. Pectoral 

 lins free, placed low. Ventral iins ubdominal, many-rayed, provided in 

 the male with claspers. Dorsal fin usually divided ; anteriorly with a 

 very strong spine, which is grooved behind. Caudal lin low, fold like. 

 Skin naked, rarely somewhat i)rickly. Lateral line present, usually 

 with numerous branches anteriorly. Three free gOls and two half gills, 



