FISHES OF THE GULF OF MAINE 9 



Key F — Continued 



19. The caudal peduncle is slender and has a conspicuous longitudinal keel on either side; the pectoral fins do not reach 



back as far as the point of origin of the dorsal fin Pilotfish, p. 372 



The caudal peduncle is deep and has no longitudinal keel; the pectoral fins reach back farther than the point of 

 origin of the dorsal fin 20 



20. There are 6-8 short detached spines, each with a small triangular fin membrane, on the back in front of the dorsal 



fin Barrelfish, p. 369 



There are no detached spines on the back in front of the dorsal fin 21 



21. The ventral fins stand far behind the bases of the pectoral fins; the point of origin of the dorsal fin is little if any in 



advance of the anal fin; the pectoral fins (Gulf of Maine species) are very long, reaching back nearly to the base 



of the tail fin Flying fish, p. 172 



The ventral fins stand about under the base of the pectoral fins; the point of origin of the dorsal fin is far in ad- 

 vance of the anal fin; the pectoral fins are small, falling far short of the anal fin Black ruff, p. 370 



KeyG 



Fishes as in Key F, except that at least the forward one-third of the single dorsal fin is spiny. There is no adipose fin 

 behind the rayed dorsal nor fleshy flap in front of it (from No. 26, p. 6). 



1 . The body (tip of snout to base of caudal fin) is at least as deep as it is long Boarfish, p. 438 



The body is considerably longer than it is deep 2 



2. The rear part of the dorsal fin is soft-rayed .3 



The whole length of the dorsal fin is spiny 8 



3. Sides of head bony, with knobs or spines 4 



No knobs or spines on the sides of the head 5 



4. Sides of head armed with conical spines; the spiny portion of the dorsal fin is at least as long as the soft part; the 



body is flattened sidewise Refer to Rosefish family, key, p. 430 



Sides of head with low rounded knobs only; the spiny portion of the dorsal fin is considerably shorter than the soft 

 part; body tadpole-shaped Arctic sculpin (Sculpin family in part), p. 453 



5. The ventral fins are much larger than the pectorals; the eyes are very large Short big-eye, p. 410 



The ventral fins are not larger than the pectorals; the eyes are not very large 6 



6. The pectorals are sharply pointed; the body is much flattened sidewise Refer to Porgy family, key, p. 411 



The pectorals are rounded; the body is not much flattened sidewise 7 



7. The rear (soft) part of the dorsal fin is nearly as long as the front (spiny) part; the anal fin is much higher than 



long Seabass (Seabass family in part), p. 407 



The rear (soft) part of the dorsal fin is less than half as long as the spiny (front) part; the anal fin is longer than 

 high Refer to Cunner family, key, p. 473 



8. The mouth is strongly oblique; there are no ventral fins Wrymouth, p. 500 



The mouth is not strongly oblique; ventral fins are present (very small in one species) . .Refer to Blenny fishes, key, p. 491 



THE CYCLOSTOMES. CLASS AGNATHA 



The lampreys are the most primitive of the appearance, but are easily distinguishable from 



true vertebrates, their skeletons being cartilagi- the true eels and, indeed, from most of the true 



nous without any true bone, and their skulls fishes, by their peculiar jawless sucking mouth 



hardly differentiated from the vertebral column situated at the tip of the snout, and, further, 



which forms a simple notochordal sheath. They from all Gulf of Maine eels by lacking pectoral 



have no true jaws, no ribs, no shoulder or pelvic fins, 

 girdles, and no paired fins. They are eel-like in 



THE HAGFISHES AND LAMPREYS. FAMILIES MYXINIDAE AND PETROMYZONIDAE 



These two groups are easily distinguished, one nally, whereas the lampreys have no barbels, their 



from the other, by the fact that the hags have mouths are disc- or funnel-like, their eyes are well 



several barbels on the chin, that their mouths developed after the larval stage is past, and they 



are not disc- or funnel-like, that they have only have one or more dorsal fins separate from the 



one continuous fin fold on the back and around caudal fin. 

 the tail, and that their eyes are not visible exter- 



