PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 559 



Pectoral tins normally situated on the scapular cincture, and with its 

 lower rays branched. 



Ventral fins thoracic, each with a spine and five rays, the first or sec- 

 ond of which is longest. 



The vertebrte number 24—10 abdominal and 14 candal; their bodies 

 are compressed and higher than long. The first two are specially mod- 

 ified : (1) The first has its central portion directed downwards, and its 

 articularfacets for the exoccipitals nearly vertical and directed forwards; 

 its spine fits into the second neural spine. (2.) The second vertebra 

 has a very short body, compressed antero-posteriorly, and its spine is 

 erect, and with the basal portion expanded forwards. The other verte- 

 brie are gradually modified. 



The anterior zygapophyses are well developed, as are also the poste- 

 rior of the caudal. vertebr?ej and about the middle the posterior partly 

 overlap the anterior of the succeeding ; inferior zygapophyses are ru- 

 dimentary ', the neurapophyses and neural spines arise direct from the 

 anterior margins of the vertebra, and those of the middle of the column 

 (e. </., 7 to 16) are erect, while the hindmost gradually decline back- 

 wards; the parapophyses of the third to ninth vertebrae arise near the 

 inferior surface of the vertebral bodies, are well developed, spiniform, 

 and are all directed downwards and outwards, and partly (7 to 10) with a 

 haimal canal ; those of the tenth are expanded at their base externally, 

 and their i)oints converge and repose in the first htemal spine ; the first 

 hffimal spine is grooved in front and somewhat expanded mesially. The 

 sockets for the ribs are on the sides of the centra and at the external 

 bases of the (third — eighth) parapophyses. 



These characters have been formulated on comparison of specimens in 

 alcohol and skeletons of Chcctodipterus faber with those of Chretodon- 

 tids, Serranids, Pristipomatids, &c. The resemblance to the Chaeto- 

 donts (e- ry., Chwtodon or Fomacanthus lyaru) is much greater than to any 

 other. Chcetodipterus differs from most fishes, and resembles the typical 

 Chaitochmtids in the specialization of the two foremost vertebne, the 

 great development of the parapophyses, and the inferior position of the 

 sockets for the ribs. The. skull likewise resembles that of the Chieto- 

 dontids in general characters, and especially in the oblique occipito- 

 spheuoid axis and the development of the exoccipital condyles. In 

 fine, the Ephippiids are very closely related to the Chaitodontids, but 

 may be distinguished as follows: 



Cha^-todontoidea with a wide scaly isthmus extending fiom the pec- 

 toral region to the chin and separating the branchial apertures ; spinous 

 partially differentiated from the soft portion of the dorsal ; upper jaw 

 scarcely protractile; ethmoid cariniform above (not sunk and concave) 

 and vomer declivous (not projecting forwards or refuse), parapophyses 

 spiniform and, posteriorly inclosing a htemal canal, and post-temporal 

 bones bifurcated. 



Only two genera certainly belong to the family, Ephippus Cuv. 



