306 
the skull, and the gill openings are more than 
a skull length from its posterior border. The 
peculiar basketlike arrangement of the 
branchiostegal rays has doubtless been de- 
veloped in ophichthids to shield this other- 
wise unsupported area of the gill arches. It 
seems anomalous that a similar arrangement 
has not been developed in other eel families 
with posteriorly placed gill arches. 
The auditory bulla, though variable in the 
Ophichthidae, is always present. No trace of 
this structure is visible externally in the skull 
of Conger. 
The pectoral girdle is less degenerate 
(hence more primitive) in Conger, which re- 
tains four actinosts, than in ophichthids, in 
which one actinost at most has been found 
and in which the girdle may be reduced to a 
clei thrum and supraclei thrum. 
Regan’s chief osteological differentiation 
( 1912 ) between the Congridae and Ophich- 
thidae lay in the vestigial neural spines of the 
latter family. In addition, the intermuscular 
bones of ophichthids are well developed, and 
the pleural ribs are often laminar. 
From this comparison it is plain that the 
Ophichthidae and Conger are very well 
separated. If other genera of the Congridae 
or other eel families are more closely related 
to the Ophichthidae, there is nothing in the 
literature to indicate it. 
Within the Ophichthidae several minor 
lines of evolutionary development seem to be 
represented. It seems justified on zoological 
grounds (as well as from precedent) to remove 
Muraenichthys, subfamily Myrophinae, first 
(Gosline, 1950). This genus has two primi- 
tive features not found in the other genera 
examined: the dorsal and anal form an ex- 
ternally visible fin around the tip of the tail, 
and, in M. cookei at least, the suspensorium 
is somewhat forwardly directed. M. cookei 
also has a moderately short skull with round- 
ish interorbital opening, and the ethmoid 
projects over the frontals as a rather broad, 
bilobed plate. In these two features Muraen- 
ichthys disagrees with Conger and with all but 
PACIFIC SCIENCE, Vol. V, October, 1951 
Myrichthys of the Ophichthidae examined. 
Within the subfamily Ophichthinae, one 
specialized group contains Brachysomophis and 
probably also Ophisurus (or Oxystomus). These 
two genera have developed, probably via 
Ophichthus, a protruding lower jaw, fanglike 
teeth, and an extremely long maxillary sup- 
ported (as in some muraenids) by a strut of 
postorbital ossicles. These characters are 
probably all functional adaptations for fish- 
eating. In other respects (as well as in the low 
vertebral number) the skull of Brachyso- 
mophis resembles that of the weak- jawed 
Caecula. 
Another group that can immediately be 
separated from other Ophichthinae contains 
Myrichthys and probably Callechelys. Myrich- 
thys (Fig. 5) has a relatively short, high skull, 
vertically elongate interorbital opening, large 
orbitosphenoid, and broad, emarginate pos- 
terodorsal ethmoid projection. In these char- 
acters Myrichthys resembles Muraenichthys, 
though convergent evolution rather than 
close relationship would seem indicated. At 
any rate, Myrichthys and Callechelys differ from 
Muraenichthys and most other ophicththids in 
the large number of vertebrae and in having 
the relatively high dorsal commencing far 
forward on the head. 
The remaining genera studied are all rather 
similar internally, though a Machaerenchelys- 
Leiuranus-Phyllophichthus group can be easily 
separated on tooth characters. In these three 
genera the vomerine teeth are few or absent 
and are replaced functionally by those of the 
maxillaries which have moved in toward the 
center of the upper jaw. 
The last three genera to be dealt with are 
Caecula, Cirrhimuraena, and Ophichthus. Prob- 
ably these are not closely interrelated, but 
I cannot place them with other generic 
groups. Caecula itself may be composite, as 
it is characterized merely by having the fins 
rudimentary or absent. (Jordan and Ever- 
mann [1896: 374] state, on what basis I do 
not know, that Sphagehranchus [ = Caecula] 
"is the most simple in structure among the 
