396 
PACIFIC SCIENCE, Vol. XX, October 1966 
in g off early in its history. Another lineage may 
be represented by those forms having C4 con- 
tacting B4, including Caecula and Bascanich- 
thys. The remaining genera, Leiuranus Phyl- 
lophichthus, Machaerenchelys, and Callechelys 
are generally similar and have no trace of C5. 
Whether they might be more closely related 
to one or the other of the groups suggested 
above cannot therefore be commented on. 
Among most members of the subfamily 
Echelinae the gill arch skeleton is severely 
reduced and approaches the form characterizing 
the muraenids. Echelus, however, is a notable 
exception, for its gill arch skeleton is perhaps 
the most generalized of any of the ophichthids 
examined (Table 1). 
Among echeline eels there is a tendency for 
the lower pharyngeal tooth plates to be some- 
what anteriorly displaced in the more special- 
ized forms. In Echelus they occupy a position 
similar to that of the tooth plates of Conger 
and are supported by C5. Schultzidia (Figs. 11, 
16) has the tooth plates posterior in position, 
supported by C4. Muraenichthys cookei (Figs. 
12, 13) has them more forward and M. 
laticaudata still more so. In Ahtia and Lepten- 
chelys (Figs. 14, 15) the tooth plates are very 
elongate, far forward in position, separating 
the ventral parts of the third arch on either 
side. In their high degree of specialization 
Ahlia and Leptenchelys bear some resemblance 
to the group characterized by U ropterygius of 
the Muraenidae (Table 1, Fig. 41). 
There has been continuing discussion of 
intergeneric relationships between echeline eels, 
much of which has concerned the limits of 
the genera My r op his and Muraenichthys (Parr, 
1930; Myers and Storey, 1939; Myers and 
Wade, 1941 ; Wade, 1946; Schultz and Woods, 
1949; Gosline, 1950, 195 la, 1951 h; Schultz, 
1953; Bohlke, 1956, I960; Nelson, 1966). On 
the basis of gill arch characters the relationships 
Figs. 11-20. 11, 16, Schultzidia johnstonensis. 12 and 13, Muraenichthys cookei. 14 and 15, Lepten- 
chelys labialis. 17 and 18, Leiuranus semicinctus. 19 and 20, Caecula platyrhyncha. 
