222 ZOOLOGY. 
Another genus of Percoids, Holocentrum, has brilliant and denticulated 
scales, a spinous and denticulated operculum, and a preoperculum, with a 
well developed spine, projecting posteriorly. A species, H. longipinne 
(pl. 83, fig. 1), is found in the American waters. The genus Sphyrena has 
a greatly elongated body, with two separated dorsals. Lower jaw longer 
than upper: both with strong teeth. Ventrals posterior to the pectorals. 
A species of this genus, S. barracuda, is found on the southern shores of 
the United States, particularly about the Florida reefs, where it is more 
dreaded for its ferocity than the shark. It is there called barracuda pike, 
or barracuda, and attains a length of six or seven feet. Sphyrena spet, a 
Mediterranean species, is figured in pl. 83, fig. 4. A species of Trachinus, 
T. draco, sea-cat, or weever (pl. 81, fig. 12), is much feared for the 
injuries it can inflict with its spinous dorsal. A special regulation in 
France requires that these spines be cut off before the fish is exposed to 
sale. It has not yet been found in American waters. Acerina constitutes 
a genus of fresh-water fish, allied to the true perches, but has a single 
dorsal fin. Of two species, both European, A. cornua, or the ruffe, is found 
in various waters of England and the continent. Its flesh is well esteemed, 
but the fish never attains to a large size. Figured in pil. 83, fig. 10. The 
genus Mullus, or mullet, has two separated dorsals, and two cirri at the 
symphysis of the lower jaw. The genus is not found in America. Pl. 85, 
jig. 7, represents M. barbatus. 
The next family is that of the ScLErocEnIpa, or TrieLtipé, with the head 
spined and armed in various ways. The suborbital bone is extended more 
or less backwards, and articulated to the preoperculum. The genus 
Trigla has the operculum and shoulder-plate running out backwards in a 
spine ; seven branchiostegous rays, and three detached rays at the base of 
each pectoral fin. Trigla lyra, or the piper (pl. 83, fig. 7), is a rather 
rare HKuropean species. JT. cuculus occurs on the coast of the United 
States. More American species are found in the genus Prionoius, closely 
allied to Trigla. Dactylopterus has the detached filament of Trigla 
greatly elongated, so as to exceed in length the fish itself, and united by a 
fin by means of which it can be sustained in the air for a short period of 
time. The best known species is D. volitans, or flying-fish, and is shown 
in pl. 88, fig. 12. There is another flying-fish, Hzxocetus, belonging to the 
Eisocide, which is a better flyer than Dactylopterus. The genus Cottus 
has a variously-armed head, which is large and depressed ; teeth in both 
jaws, and on the front of the vomer; branchiostegous rays six; two dorsals, 
distinct or but slightly connected, ventrals small. Two distinct types of 
this genus exist, one with the head strongly armed with spines of various 
kinds, and the other with the spines few in number, and nearly obsolete. 
The latter are all fresh water, the former marine. Numerous species 
of fresh water Cotlws occur both in Europe and America, all closely 
xesembling each other. They may be distinguished geographically by the 
fact, that while the small subcutaneous plates along the lateral line are 
continued out to the tail in the European species, in the American they 
cease within a short distance (one fourth, perhaps) of the total length, and 
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