46. SALMONID^ — MICROSTOMA. 
289 
dd. Scales larger, similar in botli sexes; pectoral rays 10-12. 
e. Teeth feeble, those on tongue very weak; scales small, adherent. 
Tiialeiciitiiys, 141. 
ee. Teeth stronger, those on tongue enlarged ; scales moderate, decid- 
uous OSJIERUS, 142. 
cc. Ventrals inserted under or behind the middle of dorsal; mouth moderate 
or small. 
/. Scales cycloid. 
• g. Jaws with minute teeth ; maxillary reaching past front of eye. 
IIypomesus, 143. 
gg. Jaws toothless; maxillary not reaching front of eye. 
Argentina, 144. 
jf. Scales ctenoid IlYPirALONEDRU.s, 145. 
** Pyloric coeca many; stomach siphonal. 
1 Jaws toothless or with a few fee*ble asperities; scales rather largo; anal fin 
somewhat elongate; m.axillary short and broad ; not au- 
adromous {Coregonince) Coregonus, 146. 
tt Jahs with distinct teeth; scales mostly small. {SalmonincB.') 
h. Dorsal fin very long and high, of about 20 rays; scales mod- 
erate; tongue toothless ; not auadromous. 
Thymallus, 147. 
hh. Dorsal fin moderate, its rays 9-15 in number; tongue with 
teeth. 
i. Dentition very feeble, incomplete ; anal fin elongate, of about 
17 rays; scales moderate; not auadromous. 
Stenodus, 148. 
it. Dentition strong and complete; conical teeth on jaws, vo- 
mer, and palatines ; tongue wfth two series of strong 
teeth (deciduous in very old specimens of Oncorhgtichus)-, 
scales small. 
J. Anal fin elongate, of 14-17 rays; vomer narrow, long, flat, 
with weak teeth; species black spotted. 
Oncorhynchus, 150. 
ij. Anal fin short, of 9-11 developed rays. 
k. Vomer flat, its toothed surface plane; teeth on the shaft 
of the vomer in alternating rows or in one zigzag row, 
those on the shaft placed directly on the surface of the 
bone, not on a free crest (posterior vomerine teeth some- 
times deciduous) ; species black spotted Salmo, 151. 
Jck. Vomer boat-shape<l, the shaft strongly depressed, with- 
out teeth; very small, about 200 in the course of the lat- 
eral line; species not anadromous, spotted with red or 
gray Salvelinus, 152. 
13§,— MICROSTOMA Cuvier. 
(Cuvier, Rl^gne Anim. ii, 1817: type Gasferopclecus microstoma = Microstoma ro- 
timdatum Risso.) 
Body elongate, cylindrical, covered with large, thin, silvery scales. 
Head short. Month very small, terminal; premaxillaries very small; 
maxillaries very short and broad, not extendiag to the front of the very 
large eye, which forms more than half the depth of the side of the head. 
Lower jaw and vomer with a narrow series of fine teeth; no other teeth. 
Dorsal fin short, inserted before or behind the ventrals, which are behind 
Bull. ISiat. Mils. ISTo. IG 19 
