486 BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



Beach in 1868, and was considered by Mr. Krefft as new and unde- 

 scribed species, but unfortunately he never described it, and descrip- 

 tion is now impossible, so much painting and puttying and clipping 

 have been practised in setting up the specimen." 



Subclass HOLOCEPHALI 



Body massive, compressed. Tail and caudal region attenuated. 

 Upper jaws and other palatal cartilages joined with skull. Dental 

 plates in 3 pairs, vomerine and palatine above, mandibular below. 

 Opercles rudimentary. One gill opening each side of pharynx, con- 

 tains 4 gill clefts and 4 gills united with skin terminally. No 

 spiracles, except in embryonic stages. Skull without system of mem- 

 brane bones, as opercles, suborbitals, etc. Skeleton cartilaginous. 

 No distinct suspensorial cartilage for lower jaw. Vertebrae imper- 

 fect, coalescent anteriorly. Brain massed posteriorly, more dis- 

 tributed forward, hemispheres distant from optic lobes and attached 

 to them by nerve-like thread. Intestine with spiral valve. Skin 

 naked, muciferous system highly developed. Dorsal fin erectile, with 

 spine. Pectorals normal, low. Ventrals abdominal. Mature males 

 with erectile frontal tentacle and prepelvic claspers. 



The living chimaeroids are a divergent and modified branch of 

 some primitive sharklike type. Besides certain characters of the bony 

 fishes they have acquired others distinctively their own. Their rela- 

 tion to the elasmobranchs is seen in their cartilaginous skeleton, 

 dermal denticles, the brain structure and especially the reproductive 

 organs. The large eggs and their enclosure in horny coverings is 

 another interesting feature in common. The single gill opening 

 is modified toward the bony fish type, also the structure of the gill 

 filaments, the presence of an opercle, the rectum opening externally 

 before the urino-genital apertures and not into a cloaca. 



Six families are admitted and of these three are represented by a 

 few living forms. The fossils are, however, very numerous and date 

 from Paleozoic time. As but few forms are known outside the Indo- 

 Pacific I have included all the living forms, based chiefly on Garman's 

 memoir. 



ANALYSIS OF FAMILIES 



a\ Chimaeeoidei. Snout prominent; soft, without proboscis; claspers trifid, 



rarely bifid Chimaeridae 



o^ Caixoehinchoidei. Snout produced, more or less as proboscis ; claspers 

 simple. 



b\ Snout produced in long simple beak Ehinochimaeridae 



6^ Snout produced into leaf-shaped flexible appendage Callorhinchidae 



