400 
PACIFIC SCIENCE, Vol. XX, October 1966 
Figs. 31 - 40 . 31 and 32, Anguilla rostrata. 33 and 34, Moringua javanica. 33 and 36, Dysommina rugosa. 
31 and 38, Chilorhinus platyrhynchus. 39 and 40, Kaupichthys diodontus. 
Fed, although reduced in Kaupichthys. Among 
muraenids it is lost as an independent element. 
Dorsally, the skeleton is complete in terms 
of number of elements in Heterenchelys, An- 
guilla, Moringua, Chilorhinus, Chlopsis, and 
Kaupichthys hrachychirus. 12 is rudimentary in 
K. diodontus (Fig. 39) and absent altogether 
in Dysommina (Fig. 35) and the muraenids 
(Fig. 44). In Dysommina there is but a single 
upper tooth plate, probably representing a 
fusion of the two present in more generalized 
forms. In the muraenids the tooth plate is like- 
wise single and apparently has fused with 13. 
On the basis of gill arch characters, the xeno- 
congrids, Dysommina, and the muraenids 
resemble one another more than they do other 
members of the lineage to which they presum- 
ably belong. Dysommina in this regard 
resembles the xenocongrids in having C5 well 
developed and the lower pharyngeal tooth 
plates rather small and posterior in position, 
with small conical teeth in numerous rows. It is 
more generalized in having the hypobranchials 
interconnected, but more specialized in having 
lost 1 2 altogether and having the upper pharyn- 
geal tooth plates in a single pair, as in the 
muraenids. For these reasons the arches of 
Dysommina seem intermediate in structure be- 
tween those of the xenocongrids and muraenids 
(cf. Ginsburg, 1951; Bohlke and Hubbs, 
1951). 
Within the Muraenidae two structural types 
are apparent: one (Fig. 41), including only 
Uropterygius, Anar chi as, and Channomuraena, 
has independent hypobranchials in the first and 
second arches. The lower pharyngeal tooth 
plates lie generally on the dorsal surface of the 
proximal end of C4. The other type (Fig. 42), 
