Classification of the Order OstariojJiijsi. -fW 



Stronf,' anterior canines; lateral teoth pom- 

 pressL'd, pointed, buL-kwardly directed, 

 uni- or bicuspid, uuiscrial, witii or with- 

 out minute inner teeth ; praeniaxillary 

 dwurved posteriorly, excluding the max- 

 illary from the j-'ape Ichf/ii/oborns, Menvborus, 



^ cohorus. 



Division 2. G Y M X T I F R M E S *. 



These Neotropical fishes differ from the Characiforraes 

 externally in the short prtecaudiil region and anterior vent, 

 long tapering tail, with the anal fin much extended and the 

 caudal reduced or absent, absence of dorsal and pelvic tins, 

 and restricted oill-openings. The mouth is non-prctraclile 

 and the niaxillaries enter tiie gape. In cranial osteology the 

 Gymnotitornies closely resemble the Characidie, but the 

 opisthotic is absent ; palatine and pterygoid bones are absent, 

 but the other members of the hyopalatine series are well 

 developed (PI. II. fig. 3), and the mesopterygoid forms an 

 extensive union with the parasphenoid and vomer. The 

 suboperculum is reduced or absent. The post-temporal is 

 simj)le; the coracoids show considerable ditrerences in struc- 

 tnre and development within the group. Tlie vertebral 

 column is similar to that of the Chamcitormes ; the centra of 

 the first four vertebrje remain distinct and the anterior ribs 

 are inserted on autogenous parapojihyses. The anterior and 

 posterior divisions of the air-bladder are connected by a 

 narrow duct f. 



The principal characters of the families and subfamilies 

 are shown in the following synopsis : — 



I. Maxillaries well developed, larger than praemaxillaries. Hypo- 

 coracoid >-shaped, the slender lower fork running downwards 

 and forwards to the cleithrum ; pectoral radials 4. Anterior 

 nostril superior ; vent below the head ; mouth usually small ; 

 dentition varied. Body scaly, compressed ; no electric organs ; 

 orbitosphenoid and alisphenoids well developed. 



A. Mesocoracoid well developed ; lower limb of hypocoracoid meet- 

 ing cleithrum near the symphysis ; anterior part of air-bhidder 

 enclosed in a bony capsule ; mouth toothless ; maxillary articu- 

 lated with distal end of pnemaxillary ; uo caudal ; no adipose 

 tin 1. Ithamphichthjjidce. 



* Eigenmann and Ward, Proc. Wasliingtou Acad. vii. 1900, p. lo9, 

 give a systematic account of tlie genera and species. 

 t lieinhardt, Arch. f. Naturg. 1854, p. 159. 



