128 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
filamentous, about one-fourth longer than head and nearly reaching base of caudal ; the first dorsal 
ray about 2 in the last one; pectoral lj- in head, reaching base of ventrals; ventrals short, reaching 
only half way to vent, their length 1£ in pectorals; anal rays short, base of fin 1^- in head; scutes 
moderate; caudal widely forked, the lower lobe the longer; scales large, thin, deciduous, somewhat 
crowded anteriorly ; accessory scales at bases of pectorals and ventrals ; base of caudal with small 
scales. Color, bluish-black or dark olivaceous on back and sides to level of the jet-black humeral 
spot; rest of sides and under parts bright silvery; dorsal and caudal dusky; other fins plain. 
The cotypes from Grand Plains Bayou are 2 females with ripe roe. They are 4| and 5-J- inches 
long, respectively, and differ from the types only in the deeper body and the much darker coloration 
of the upper parts. 
The amount of variation in this species, shown by the material at hand, is exhibited in the 
following table: 
No. 
Head. 
Depth. 
Eye. 
Snout. 
Max. 
Dorsal. 
Anal. 
Scutes. 
Scales. 
Locality. 
1 
ih 
3 
n 
5| 
31 
I, 12 
. I, 24 
16 + 11 
40-15 
Grand Plains Bayou, Miss. 
2 
4 
2| 
34 
51 
31 
I, 12 
I, 24 
16 + 11 
42-15 
Do. 
3 
4 
3 
3 i 
51 
31 
I, 12 
I, 24 
16 + 10 
42-14 
Melville, La. 
4 
3j! 
3 1 
3 1 
54 
31 
I, 12 
I, 24 
17 + 10 
42-15 
Do. 
5 
3g 
3 
4 
5 
3? 
I, 12 
1, 24 
16 + 11 
43-15 
Do. 
G 
31 
3 
31 
54 
3 
I, 12 
I, 24 
16 + 10 
41-15 
Grand Plains Bayou, Miss. 
7 
3 & 
3 
34 
5 
31 
I, 12 
I, 24 
17+ 9 
41-15 
Do. 
8 
3J 
3 
34 
3 
I, 12 
I, 24 
17+ 9 
41-15 
Black Bayou, Miss. 
9 
2§ 
34 
54 
3 
I, 12 
I, 24 
17+9 
40-15 
Do. 
This species appears to be rather common in the larger lowland streams and bayous of Louisiana 
and Mississippi. It probably does not reach a large size, adult examples being less than 6 inches long. 
It is not used as food, hut is of considerable value as bait in the catfish fishery of the Atchafalaya 
Eiver and its connecting lakes and bayous. 
Etymology, atchafalayos, from the type locality. 
6. Corythroichthys cayorum, new species. (PI. 7, fig. 7.) 
Type, a male 31 inches long, No. 48784, U. S. N. M. Cotype, a male, 31 inches long, No. 526, 
U. S. F. C. Type locality, near Crawfish Bar, Key West, Florida, where 3 specimens were obtained, 
October 19, 1896, by Evermann & Kendall. 
Head 8f; depth 12 1; snout 31 in head; eye 4+ D. 21 rays, on 11 + 3i rings ; A. 3, on first caudal 
ring; C. 10; P. 10. Rings 17 + 26 = 43. Body short and stout; head short, snout very short; tail 
but little longer than head and trunk. Cranial ridges strong; a high, sharp keel on snout, the occi- 
pital keel very high, its edge convex, notched near the middle, not continuous with keel on snout ; 
a strong supraocular ridge, beginning opposite posterior end of nasal keel and continuing backward 
with one hiatus upon upper edge of opercle; just below this on the opercle another longer but 
scarcely stronger ridge ; another short ridge on anterior part of opercle at level of lower part of eye ; 
opercles very convex, as if swollen outward ; keels on body and tail all strong ; the 2 lateral keels 
on body terminating on third caudal ring; the 2 lateral keels on tail beginning on the last body 
ring, thus overlapping the body keels; median keel on side well developed, terminating on sixteenth 
body ring; ventral keels strong; abdominal keel very strong. Egg-sac on first 18 caudal rings. 
Color yellowish- brown, with darker punc'tulations ; tip of snout white ; cheek, throat, and under parts 
of snout white, crossed by about 7 or 8 irregular brownish bars extending downward and backward; 
opercles brown ; fins pale. 
This species is related to C. albirostris of Heckel, differing from it chiefly in the shorter snout, 
smaller dorsal, and fewer rings. The genus Corythroichthys, established by Kaup in 1856, seems to 
be well distinguished from Sipliostoma by the strong keel on the top of the head, the strong oper- 
cular ridges, the short, stout body with prominent angles, and the very short snout. As thus defined, 
Corylliroichthys contains two species besides the one here described, viz, C. albirostris Heckel and 
C. cayennensis Sauvage. 
Etymology, cayorum, of the Keys; from Cayo Huesoy Bone Key, the original Spanish name of the 
island of Key West. 
