FISHES OF CHESAPEAKE BAY 
41 
(m) Head rough, bony, with spines, shields, and ridges. 
(n) Head rather high, compressed; interorbital space deeply 
concave; numerous fleshy cirri on head; pectoral fins mod- 
erately large, not especially produced and not divided 
into two sections .-Hemitripteridx (sea ravens), p. 309 
(nn) Head low, blunt, depressed, quadrangular, or nearly 
entirely covered with bony shields; interorbital not 
deeply concave; no fleshy cirri; pectoral fins divided into 
two sections, the inner one greatly produced, used as an 
organ of flight, _ Cephalacanthidx (flying gurnards) , p. 316 
(mm) Head not especially bony, with or without a few spines, 
no bony shields. 
(o) Body robust, depressed anteriorly, compressed poster- 
iorly; mouth large, broad; teeth short but very strong; 
scales wanting (in Chesapeake specimens); dorsal fins 2, 
the first with two or three low spines; ventral fins 
well developed, jugular, without a true spine 
Batrachoididx (toadfishes) , p. 337 
(. oo ) Body moderately or greatly elongate, more or less 
compressed; mouth usually small; teeth various; 
skin naked or with small scales; dorsal fin single, the 
anterior part and sometimes the whole fin with spines; 
ventral fins small, jugular, composed of I, 1 to 3 rays 
Blenniidx (blennies), p. 332 
0 ooo ) Body elongate, somewhat compressed, tapering both 
anteriorly and posteriorly, the caudal peduncle being 
very long and slender; mouth moderate, oblique; 
skin naked or with vertically oblong plates on sides; 
middle or sides of abdomen shielded by the produced 
innominate bones; dorsal fin preceded by two or more 
free spines; ventral fins thoracic to subthoracic, with 
one strong spine and one or two rudimentary soft 
rays Gasterosteidx (sticklebacks), p. 178 
AAA. Ventral fins absent. 
a. Body very elongate, rounded, snakelike; premaxillaries rudimentary or wanting. 
b. Body covered with rudimentary, elongate, imbedded scales, placed at right angles to 
each other; lower jaw projecting; origin of dorsal far behind pectorals 
Anguillidx (common eel), p. Ill 
bb. Body scaleless; upper jaw prpjecting; origin of dorsal over or somewhat behind middle 
of pectorals Congridx (conger eels), p. 116 
aa. Body not snakelike; premaxillary bones present. 
c. Gill membranes not joined to the isthmus. 
d. Body rather deep to very deep and strongly compressed; mouth small; caudal fin 
deeply forked; size rather small Stromateidx (butterfishes) , p. 210 
dd. Body very elongate, compressed, band-shaped, tapering posteriorly; head sharply 
pointed; mouth large, nearly terminal; teeth very large; scales wanting; dor- 
sal fin beginning on head and extending over entire body; caudal fin wanting 
Trichiuridx (cutlass fishes), p. 208 
ddd. Body moderately elongate, not compressed; upper jaw greatly produced, forming 
a sword; caudal fin large and forked; size very large 
Xiphiidx (swordfishes) , p. 209 
cc. Gill membranes broadly joined to the isthmus. 
e. Body inclosed in a bony armor composed of rings or polygonal plates. 
