398 
PACIFIC SCIENCE, VoL XX, October 1966 
1903), mark the course of the supraorbital 
canal. The interorbital pore arises from an in- 
terorbital commissure by way of a median dorsal 
opening in the frontal bones. The postorbital 
pore, those pores below the eye, and those 
between the nostrils mark the course of the 
infraorbital canal. Those on the lower jaw and 
over the preopercle mark the course of the 
preoperculo-mandibular canal. 
M. gymnotus (Fig. 22) is close to the basic 
pattern, differing only slightly in the position 
of a few pores. The three below the eye are 
somewhat posteriorly displaced. The three over 
the preopercle form an angle perhaps a little 
less than 90 degrees. 
M schultzei (Fig. 23) diverges more signif- 
icantly, having the nostrils close together and 
only a single pore between them. The three 
pores over the preopercle form an angle con- 
siderably greater than 90 degrees. 
Schultzidia johnstonensis (Fig. 24) likewise 
has a single pore between the nostrils. There 
are but two pores over the preopercle. 
Leptenchelys labialis (Fig. 25) has the pore 
system the most reduced, lacking the median 
interorbital pore, one of the three below the 
eye, two of the usual live along the lower jaw. 
The three over the preopercle form an angle 
greater than 90 degrees. The pattern of L. 
labialis seems similar to that of L. pinnaceps 
(Schultz, 1953: Fig. 16), but both of these 
differ markedly from that of L. vermiformis 
(Myers and Wade, 1941: PL 10), which has 
a greater number of pores behind the eye and 
along the lower jaw. In this regard, it has 
recently been discovered that the Central Pacific 
eels described in the genus Leptenchelys by 
Schultz (1953) are probably not congeneric 
with Leptenchelys vermiformis Myers and 
Wade, the type of the genus (Rosenblatt, per- 
sonal communication). 
Neenchelys buitendijki (Nelson, 1966: Fig. 
1 A) has only two of the usual three pores over 
the preopercle. The series along the lower jaw 
number seven-eight, instead of five. The other 
pores have the same basic arrangement as in 
M. cookei. 
In all the specimens examined the only vari- 
ability in pore number and position occurred in 
the pores of the lower jaw. The specimen of S. 
johnstonensis from Johnston Island has six 
pores on each side. The specimen of M. lati- 
caudata from Aitutaki has six on the right side 
and five on the left. 
Ahlia, M. schultzei , and Schultzidia have 
lateral line pores generally restricted to the 
trunk, numbering about 40-70. In all other 
species examined lateral line pores number 
nearly or over 100 and extend well onto the 
tail. 
The present author agrees with Schultz 
(1953:61) "that recognition of echelid genera 
must be done on a world-wide basis and not on 
the study of local fauna." However, on the 
basis of this study, Echelus, Myrophis , Ahlia, 
Muraenichthys, Neenchelys, Leptenchelys, and 
Schultzidia might be considered valid genera. 
Ahlia seems distinct from Myrophis on the 
basis of gill arch characters. It differs in gill 
arch structure also from M. schultzei and 
Schultzidia, although in all three the dorsal 
origin is posterior to the anus and lateral line 
pores are generally absent from the tail. Within 
the genus Muraenichthys, M. cookei, M. lati- 
caudata, and M. macropterus seem quite similar 
and may be representatives of a generalized 
stock having given rise to separate offshoots in 
M. schtdtzei and M. gymnotus. M. schultzei 
and Schultzidia share some characters as noted 
above. The specialized jaws and teeth (Gosline, 
1951^) and distinctive pharyngeal tooth plates 
(Figs. 11, 16) of Schultzidia would seem to 
rule out any close relationship with M. schultzei. 
Leptenchelys shows no great similarity with any 
of the other species examined. Its gill arches are 
perhaps most similar to those of Ahlia, but the 
tendency toward forward displacement of the 
lower pharyngeal tooth plates is also quite pro- 
nounced in M. laticaudata. 
Synaphobranchoid Lineage 
It is possible to separate Synaphobranchus 
(Figs. 26, 27), Diastobranchus (Castle, per- 
sonal communication), Simenchelys (Fig. 28; 
see Jaquet (1920) for ventral view), and 
Dysomma (Figs. 29, 30) from other eels on 
the basis of the posteriorly directed third hypo- 
branchials. This is in contrast to the condition 
observed in other eels and bony fishes generally, 
