402 
PACIFIC SCIENCE, Yol. XX, October 1966 
Genera examined: U r op ter y gins, Anar chi as, 
Channomuraena. 
Subfamily muraeninae 
No ossified hypobranchials in branchial skele- 
ton ; lower pharyngeal tooth plates with a prom- 
inent lateral groove; retractor ossium pharyn- 
gealium muscles with an attachment to the 
vertebral column; anterior portion of dorsal 
aorta not enclosed in a canal formed by verte- 
bral processes; vertical fins not reduced, with 
rays confined to the posterior part of the tail. 
Genera examined: Echidna, Enchelycore, En- 
chelynassa, Evenchelys, Gymnomuraena, Gym- 
nothorax, Muraena, Rabula, Strophidon. 
The outstanding feature of the gill arch 
skeleton of the muraenids is the enlargement 
of the fourth arch and with the loss of C5 the 
tooth-bearing bones it comes to support. Teeth 
on these bones are enlarged, recurved, and 
generally in two rows (Popta, 1904). These 
elements form the so-called pharyngeal jaws 
(Fig. 43). 
In view of the above, the structure of the 
gill arch skeleton of the muraenids, although 
specialized, is not sufficient to warrant the sepa- 
ration of this group at the ordinal or even sub- 
ordinal level from the other eels. Rather, stages 
in the derivation of the gill arches of the murae- 
nids are suggested in the more generalized eels 
of the same lineage. These exhibit the progres- 
sive loss of some bones, the fusion of others, 
the gradual enlargement of the fourth arch and 
the dermal tooth-bearing bones it comes to sup- 
port. 
Serrivomeridae and Nemichthyidae 
The arches of Serrivomer (Figs. 45, 46), al- 
though somewhat specialized, are rather like 
those of Anguilla, especially as regards the loss 
of B3, and the form of H3. They are rather 
complete in terms of the number of elements, 
and generalized in retaining the double articula- 
tion of C4 with B4. The arches of Avocettina 
and Nemichthys (Figs. 47, 48) are somewhat 
more reduced but still relatively complete. They 
differ markedly from those of Cyema (Figs. 49, 
50), which has the branchial skeleton severely 
reduced, more so than that of any other eel 
examined. 
The systematic position of the eels of the 
families Serrivomeridae and Nemichthyidae (as 
interpreted by Bohlke and Cliff, 1956) has not 
yet been satisfactorily determined. Whether they 
are closely related families is open to some 
doubt (Trewavas, 1932:652; Berlin, 1942: 
108). The separate frontals and generalized 
gill arch characters of Serrivomer, however, 
suggest that this form may represent an early 
offshoot from the anguilloid lineage. The con- 
dition of the frontals in the Nemichthyidae is 
variable, some members having them fused, 
Figs. 45-50. 45 and 46, Serrivomer sector. 47 and 48, Nemichthys scolopaceus. 49 and 56, Cyema atrum. 
