THE FISHES OF NEW JERSEY. S3 



these, and fifth pair being typically modified into tooth-bearing 

 loAver pharyngeals. Ova small. Median and paired fins devel- 

 oped, latter with distinct rays. No claspers. 



Key to the orders, 



a. (Ganoidei.) Arterial bulb muscular, with numerous valves ; optic nerves 

 forming a solid chiasma ; air-vessel with well-developed duct ; tail 

 strongly heterocercal throughout life ; some fins usually with fulcra ; 

 ventrals abdominal. 

 h. Skeleton cartilaginous; air-vessel simple; skin with bony shields; 

 caudal forked. chondrostei 



hh. Skeleton bony ; air-vessel cellular ; scales as rhombic enamelled plates ; 

 caudal rounded. rhomboganoidEa 



aa. (Teleostei.) Arterial bulb thin, with a pair of opposite valves ; optic 

 nerves crossing, not forming a solid chiasma. 

 c. Gill-openings before pectoral. 



d. Air-vessel if present connected by an air-duct with intestinal 

 canal and persistent through Hfe ; ventrals if present abdom- 

 inal, without spines and basal segments rudimentary. 

 e. Head naked; dorsal inserted medianly or anteriorly, 



f. Vertebrae, not undifferentiated, anterior similar to others. 



g. Body not eel-like ; shoulder-girdle attached to skull 



by means of post-temporal ; maxillary perfect, rarely 



wanting; precoracoid arch present, isospondyli 



gg. Body eel-like ; shoulder-girdle not attached to skull ; 



maxillary wanting or united with palatines ; no 



precoracoid arch. apodEs 



ff. Anterior vertebra modified, co-ossified, and with os- 



sicula auditus. 



h. Maxillary perfect, not entering into a barbel. 



EVENTOGNATHI 



hh. Maxillary imperfect, forming base of long 

 barbel. nematognathi 



ee. Head scaly ; dorsal usually inserted far back ; precoracoid 

 obsolete ; anterior vertebrae unmodified ; parietal separated 

 by supraoccipital. haplomi 



dd. Air-vessel without duct in adult; ventrals without basal seg- 

 ments ; pectorals usually separated by supraoccipital. 

 i. Spines usually present in fins. 



ACANTHOPTERI 



a. No spines in fins. anacanThini 



cc. Gill-openings in axil or behind pectoral. pEdiculati 



