4? TELEOSTEI : EVENTOGNATHI. — XII. 
c. Pectoral spines moderate, the inner serree weak, not half diameter of 
spine, the outer stronger, retrorse, body elongate; coloration nearly 
uniform, the fins darker edged. 
d. Pectoral spine short and weak, about 3 in head in adult. 
61. N. exilis Nelson. Head small, rather narrow, depressed, 4 
in length; depth 6; pectoral spine retrorse-serrate without, with 6 
small teeth within; humeral process obscure; jaws subequal. A. 
14to17. L.4. Wis. to Kansas. (NV. elassochir Swain & Kalb.) 
(Lat., slim.) 
dd. Pectoral spine longer, about 2 (1% to 27) in head. 
62. N. insignis (Richardson). Head rather broad, flat and 
thin, the upper jaw projecting ; head 44; depth 6. A. 14 to 16. 
L.10. Pa. toS.C., common E. (Lat., remarkable). 
cc. Pectoral spine very strong, curved, more than half head, its posterior 
serre recurved, their length about equal to diameter of spine, the 
anterior serre small. 
e. Color much variegated; adipose fin deeply notched, but not separated 
from C. 
63. N. miurus Jordan. Grayish; top of head, tip of dorsal, 
middle of adipose fin, and caudal black, the body with four black 
cross-blotches; head not specially depressed eye 4} in head; hu- 
meral process moderate ; pectoral spine 1} to 12 in head; head 32. 
A.13 to 15. L.5. E. N.C. to Minn. and La., abundant. (pei- 
oupos, curtailed.) 
ee. Color nearly plain brownish, everywhere above covered with fine 
small dots; adipose fin almost or quite free from caudal. 
64. N. eleutherus Jordan. Head broad, flat, depressed, the 
form very much as in Leptops olivaris ; humeral process obscure; 
eye 54 in head; pectoral spine 12 to 2 in head; head 34; A. 13. 
L.4. White R., Ind., and French Broad R.; 3 specimens known. 
(ehevepos, free.) 
bb. Pectoral spine entire, grooved behind; adipose fin continuous with 
the caudal. 
65. N. gyrinus (Mitchill). Head short, broad and deep; pecto- 
ral spine 2 in head ; jaws subequal, yellowish brown, not blotched, 
but with a narrow black lateral streak, sometimes with two above 
it. A.15o0r16. L.5. Hudson R. to Minn. and La., common N. 
(yupivos, tadpole.) 
Orver XII. EVENTOGNATHI. (Tue PLecrosponpy- 
LOUS FISHES.) 
This group, defined on page 26, contains the great majority of 
the fresh-water fishes of the world. Its essential character is in 
the modification of the anterior vertebre, as in the Nematognathi, 
