Here's Jacks version 01 at 150 dpi of the butterfish
Physical description from Wikipedia: http://en.wikipedia.org/wiki/American_butterfish
Fish of this species are usually deep-bodied, flattened sideways, and somewhat circular or rounded, with blunt noses and small mouths with weak teeth. Some other characteristics of this fish are the absence of ventral fins, one long, continuous dorsal fin, long pectoral fins, and tiny, cycloid scales. The tail fin is nearly as long as the dorsal fin and deeply forked. The American butterfish is similar in appearance to its close relative, the harvestfish (Peprilus alepidotus), but can be distinguished by its much lower dorsal and tail fin.
This fish is a lead-blue color above with pale sides and a silvery belly. It often has dark, irregular spots.
It is generally 6–9 in (15–23 cm), though some individuals reach 12 in. They can weigh from 1.75–20 ounces (50–567 g).
This website also has a good description (note: looks like scientific has changed since this publication)
The most distinctive characters of the butterfish are its very thin deep body, like a flounder on edge; the fish is only about twice as long as it is deep to the base of its tail fin (the only common Gulf of Maine species of this shape), combined with a single, long, soft-rayed dorsal fin, an anal fin almost equally long, and a deeply forked tail, but no ventral fins. The absence of ventral fins separates it from the pompanos; the dorsal without obvious spines from the scup (p. 411) and John Dory (p. 297); the lack of detached dorsal spines from the triggerfishes, which are, furthermore, very different in general aspect (p. 520). And it is easily distinguishable from its relative, the harvestfish (p. 368), which is rare in northern waters, by its much lower dorsal and anal fin (compare fig. 192 with fig. 194). The dorsal fin (about 45 rays) originates close behind the axils of the pectorals and tapers at first abruptly and then gradually backward, while the anal (about 40 rays) narrows evenly from front to rear. There is a forward-pointing spine close in front of the dorsal fin, so short as hardly to be visible though it can be felt; also 3 very short spines in front of the anal, almost wholly embedded in the skin, the first of which points forward. Both the dorsal fin and the anal extend rearward almost to the base of the caudal fin.
Distinctive, also, are the long pointed pectoral fins, short head, blunt snout, small mouth, weak teeth, and the short and slender caudal peduncle, which does not have longitudinal keels. The scales are very small, and are easily detached when the fish is handled, and there is a row of very conspicuous mucous pores below the forward half of the dorsal fin.
Leaden bluish above, pale on the sides, with numerous irregular dark spots which fade after death. The belly is silvery.
The largest are about 12 inches long; the general run are about 6 to 9 inches long. The weight runs about 1¾ ounces at 6 inches, 4 to 4½ ounces at 8 inches; about 1 pound at 11 inches (if fat). The largest weigh about 1¼ pounds.
A description and illustration can be found at this website: