ut
consists of fewer bones, probably because of fusion. The scales resemble
those of _Rhabdoderma_. With regard to general shape of fin girdles, the
pectoral girdle resembles that of _Eusthenopteron_ more than that of
_Rhabdoderma_, but the cleithrum is more nearly like the cleithrum of
_Rhabdoderma_. The pelvic girdle appears to be midway between those of
_Rhabdoderma_ and _Coelacanthus_ in general appearance. Regarding the
basal plates of the remaining fins, those of _Synaptotylus_ appear to
resemble basal plates of both _Rhabdoderma_ and _Coelacanthus_.
Considering the structure of the sphenethmoid region of the braincase,
_Synaptotylus_ is probably more closely related to _Rhabdoderma_ than
to other known coelacanth genera.

COMMENTS ON CLASSIFICATIONS

Classification of Carboniferous coelacanths has been difficult, partly
because the remains are commonly fragmentary, and significant changes in
anatomy did not become apparent in early studies. In general,
coelacanths have been remarkably stable in most characters, and it has
been difficult to divide the group into families. As Schaeffer (1952:56)
pointed out, definition of coelacanth genera and species has previously
been made on non-meristic characters, and the range of variation within
a species has received little attention. For example, Reis (1888:71)
established the genus _Rhabdoderma_, using the strong striation of the
scales, gular plates and posterior mandible as the main characters of
this Carboniferous genus. Moy-Thomas (1937:399-411) referred all
Carboniferous species to _Rhabdoderma_, redescribed the genus and
compared it to _Coelacanthus_, the Permian genus. He cited as specific
characters the ornamentation of the angulars, operculars and gular
plates (Moy-Thomas, 1935:39; 1937:385). Individual variation in some
species has rendered ornamentation a poor criterion. This variation is
apparent in _Synaptotylus newelli_ (Hibbard), some specimens having
little or no ornamentation; others having much more. The number of
ridges and pattern of ridges on the scales also varies. Schaeffer
(1952:56) has found this to be true of _Diplurus_ also. Moy-Thomas
(1935:40; 1937:385) realized that the type of scale is a poor criterion
for specific differentiation. In the search for features useful in
distinguishing genera of coelacanths, Schaeffer and Gregory (1961:3, 7)
found the structure of the basisphenoid to be distinctive in known
genera, and thought it had taxon