FISHES OF HAWAIIAN ISLANDS. 
73 
Genus 40. STERNOPTYX Hermann. 
Body much elevated and compressed, passing abruptly into a short and compressed tail, the angle 
made by the hind margin of the trunk and the lower edge of the tail being tilled up by a broad fold 
of the integument, of peculiar transparent appearance, resembling thin cartilage; this fold bears the 
anal tin and is supported by interlnemal rays; head short, compressed, deep, with extremely short 
snout and a wide, subvertical mouth; eyes large, lateral; margin of upper jaw formed by maxillary 
and intermaxillary, the latter being very short, and each of these bones having a sharp edge which is 
armed with a series of very small teeth, somewhat unequal in size; lower jaw with a similar dentition; 
vomer and palatines toothless; bones of the head firm, some of them terminating in short spines, 
namely the angle of the preopercle, the postero-inferior angle of the mandible, and the symphysis of 
the humeral bones; gill-opening very wide, the gill-membrane being attached to the isthmus; gills 4, 
the branchial arches long, not angularly bent, the branchial slits being closed by a membrane in their 
upper portion; a few of the gillrakers are prolonged, needle-shaped and widely set, the others being 
quite rudimentary; pseudobranchiae present; greater portion of body scaleless, covered with a silvery 
pigment; a luminous organ occupies the inner side of the operele close to its lower end, another is 
placed at the anterior end of the ceratohyal, and finally a very large glandular mass is lodged on the 
upper edge of the anterior end of the clavicle; a series of luminous spots runs along the lower edge of 
the abdomen and is separated from the series of the other side by a cartilaginous fold occupying the 
median line of the abdomen; another series runs on each side of the isthmus, a row of 3 above and 
behind the root of the ventrals, and another row of 3 above the vent; the luminous organs on the 
lower part of tail consist anteriorly of a row of 4, of which the first is prolonged toward the back as a 
narrow band, terminating about the middle of the depth of the body in a globular black spot with a 
white center; posteriorly in front of the caudal rays there is another row of 4 small spots; the dorsal 
fin occupies the middle of the back and consists of a triangular bony lamella, very thin in front, but 
strengthened along its hind margin, and followed by several rays; adipose fin absent, or represented 
by a very low membranous fringe of the dorsal margin of the tail; the anal fin is incompletely devel- 
oped, extending from the vent to the root of the caudal fin, its rays being rudimentary, widely set, 
and scarcely free; caudal fin broad and forked; pectorals well developed, close to the lower profile; 
ventrals small, the pelvic bone with a bifid spine in front pointing forward. (Gunther. ) 
The single Hawaiian species ( Sternoptyx diaphana ) is described in Section II. 
Sternoptyx Hermann, Naturforscher, XVI, 8,1781 (diaphana). 
Order G. APODES.— The Eels. 
Teleost fishes, with the premaxillaries atrophied or lost, the maxillaries lateral, and the body 
anguilliform and destitute of ventral fins; the most striking feature is the absence of premaxillaries, 
taken in connection with the elongate form and the little development of the scapular arch, which is 
not attached to the cranium. Other characters, not confined to the Apodes, are the following: The 
absence of the symplectic bone; the reduction of the opercular apparatus and of the palato-pterygoid 
arch; the absence of ventral fins; the absence of the mesocoraeoid or prsecoracoid arch; the reduction 
or total absence of the scales; there are no spines in the fins; the gill-openings are comparatively small; 
there are.no pseudobranchiae; the vertebrae are in large number and none of them specially modified; 
the tail is isocercal — that is, with the caudal vertebrae remaining in a straight line to its extremity, as 
in the embryos of most fishes, and in the Anacanthini. 
We begin our discussion of the eels with the forms which seem nearest to the primitive stock from 
which the members of the group have descended. It is evident that among the eels the forms of 
simplest structure, Sphagebranchus, etc., are not in any sense primitive forms, but the results of a long- 
continued and progressive degeneration, so far as the fins and mouth parts are concerned. The Apodes 
are probably descended from soft-rayed fishes, and their divergence from typical forms is in most 
respects a retrogression. 
