ARTIFICIAL KEY. 27 
pp. Bones of jaws co-ossified, the maxillary with the pre- 
maxillary, the dentary with the articular. 
PLECTOGNATHI, XXII. 
oo. Pectoral fins pediculate, the basal bones reduced in number 
and elongate, the gills in their axils. PEDIcULATI, XXIII. 
More than two hundred families are now recognized among the 
true fishes. The characters on which family divisions are based 
are usually internal, and often difficult for the beginner to ascer- 
tain. ‘The boundaries and definitions of many families are also 
still uncertain. Instead, therefore, of giving a natural analysis 
under each order of the families included within it, I have thought 
it best to give instead an Artificial Key by which the student can 
recognize any of the families of True Fishes included in this work. 
For analytical keys showing, in some degree, the natural charac- 
ters, the student is referred to Jordan and Gilbert’s Synopsis of the 
Fishes of North America. A repetition of these analytical tables 
would consume considerable space, and would not be of much aid 
to any but advanced students. 
Artificial Key to the Families of True Fishes included in the 
Present Work. 
Series I, VENTRAL FINS PRESENT, ABDOMINAL. 
A. Dorsal fins two, the anterior rayed, the posterior adipose. 
B. Body naked; head with 4 to 8 sian ; dorsal and pectoral each with 
astrong spine. . . of ei Ne oy)! of (all? ol ORE DRED ae) aes 
BB. Body scaly ; no baibenss no pikes: 
C. Maxillary wanting, or grown fast to premaxillary ; head scaly. 
SYNODONTID4S, 32. 
CC. Maxillaries distinct; head naked. 
D. Scales ctenoid; cat of gs be formed by premaxillaries 
MONG sheer a iss ap epee PERcoPsIDs, 35. 
DD. Scales cycloid; mats of pee jaw formed in part by maxil- 
laries. 
£. Stomach a blind sac, with few pyloric cxca. (Smelt, etc.) 
ARGENTINID&, 383. 
LE. Stomach siphonal, with many pyloric ceca. SALMONID#, 34. 
AA. Dorsal fin single, with free spines before it; body naked, or with bony 
plates; ventralrays,I,1, . . . . . . .. GASTEROSTEIDA, 45. 
AAA. Dorsal fins two, the anterior of simple rays or spines, the posterior 
chiefly of soft rays; ventrals, I, 5. 
F. Teeth very strong, unequal; a lateral line present. SPHYR&ZNID&, 48. 
FF. Teeth small, subequal; no lateral line. 
G. Dorsal spines slender, 4 to 8; analspinel. . . ATHERINID&, 47. 
GG. Dorsal spines stout, 4; anal spines, 2or3. . . . Muaitips&, 46. 
AAAA. Dorsal fin single, of soft rays only (sometimes preceded by fulcra or 
followed by finlets). 
H. Tail evidently heterocercal. (Ganoid fishes.) 
J, Caudal forked, the lower lobe well developed. 
