THE FISHES OF NEW JERSEY: 83 
these, and fifth pair being typically modified into tooth-bearing 
lower 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. 
b. Skeleton cartilaginous; air-vessel simple; skin with bony shields; 
caudal forked. CHONDROSTEL 
bb. Skeleton bony ; air-vessel cellular; scales as rhombic enamelled plates ; 
caudal rounded. RHOMBOGANOIDEA 
aa. (Teleostet.) 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 life; ventrals if present abdom- . 
inal, without spines and basal segments rudimentary. 
e. Head naked; dorsal inserted medianly or anteriorly. 
_f. Vertebre 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 vertebre 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 vertebre 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 
vi. No spines in fins. ANACANTHINI 
cc. Gill-openings in axil or behind pectoral. PEDICULATI 
