26 TELEOSTOML 
dd. Vertebre amphiccelian (double concave); maxillary not transversely 
divided; scales cycloid. . . . . - »- «. HALECOMORPHI, X. 
aa. Arterial bulb thin, with a pair of opposite valves; optic nerves crossing, 
not forming a solid chiasma. (Series TELEOSTEI.) 
e. Air-bladder (if present) connected by an air-duct with the intestinal 
canal, this persistent throughout life; ventral fins (if present) abdomi- 
nal, without spines, their basilar segments rudimental. (Soft-rayed 
fishes.) (Physostomt.) 
Jf. Shoulder girdle attached to the skull by means of a post-temporal bone 
(suprascapula); form not eel-like. 
g. Precoracoid arch, present. 
h. Maxillary bone imperfect, forming the base of a long barbel ; no 
subopercle nor symplectic bone ; four anterior vertebra much 
modified, co-ossified, and with an ossicula auditus; supraoccipitals 
and parietals co-ossified; no scales. . . NEMATOGNATHI, XI. 
hh. Maxillary bone perfect, not entering into a barbel (rarely entirely 
wanting); subopercle and symplectic bone present. 
i. Anterior vertebre modified, co-ossified, and with the ossicula 
auaig. sx . . . » EvENroGnatut, XII. 
a. Anterior vertebrze sivailat & “ih ibang separate, and without 
ossicula auditus. . . . » % '. [.)'.'./ GsesranDyi wear 
gg. Precoracoid arch obsolete; anterior vertebre not modified; parie- 
tal bones separated by supraoccipital; head scaly. 
Hapwomyi, XIV. 
Jf. Shoulder girdle not attached to the skull; no precoracoid arch; 
parietal bones in contact; maxillary wanting or united with the 
palatines; form eel-like... .).., « «© « «.,) «| ABODEE ewe 
ee. Air-bladder without duct (in the adult); ventral fins without basal seg- 
ments, usually anterior in position; spines usually present in the fins; 
pectoral tins not on the plane of the abdomen ; parietal bones usu- 
ally separated by the supraoccipital. (Spiny-rayed fishes chiefly.) 
(Physoclystt.) 
j- Shoulder girdle connected to the skull by a post-temporal. 
k. Lower pharyngeals co-ossified; no spines; ventrals abdominal; lateral 
line on side of abdomen. . . . - . - SYNENTOGNATHI, XVI. 
kk. Lower pharyngeals separate (or united, and the dorsal fin with 
spines.) 
I. Gills tufted; pharyngeal bones and most of the branchihyals want- 
ing; skin with bony plates. . . . . LoPHOoBRANCHH, XVII. 
ll. Gills pectinate (as usual in fishes). 
m. Superior branchihyals and pharyngeals reduced in number ; 
ventrals sub-abdominal. . . . . HEmMIBRANCHII, XVIII. 
mm. Superior branchihyals and pharyngeals in normal development. 
m. Ventral fins abdominal, . . . . . . + ##PERCESOCES, XIX. 
nn. Ventral fins thoracic or jugular. 
o. Pectoral fins not pediculate, the gill openings in front of them 
p. Bones of the jaws distinct. 
g- Cranium normal. . . . . . » ACANTHOPTERI, XX. 
qq. Cranium twisted, so that both eyes are on the same side 
of head; no fin spines. . . HETEROSOMATA, XXI. 
