ore H. Eaton, Jr., for suggesting the project
and for much helpful advice. I am indebted to Dr. E. I. White of the
British Museum (Natural History) for furnishing a cast of the
endocranium of _Rhabdoderma elegans_ (Newberry) for comparison, and to
Drs. Donald Baird (Princeton University), Bobb Schaeffer (American
Museum of Natural History) and R. H. Denison (Chicago Natural History
Museum) for loans and exchanges of specimens for comparison. I am
grateful to Dr. Bobb Schaeffer for advice on the manuscript. Mr. Merton
C. Bowman assisted with the illustrations. The study here reported on
was made while I was a Research Assistant supported by National Science
Foundation Grant G-14013.

SYSTEMATIC DESCRIPTIONS

Subclass CROSSOPTERYGII

Superorder COELACANTHI

Order Coelacanthiformes

Suborder DIPLOCERCIDOIDEI

Family DIPLOCERCIDAE

Subfamily ~Rhabdodermatinae~, new subfamily

_Type genus._--_Rhabdoderma Reis_, 1888, Paleontographica,
vol. 35, p. 71.

_Referred genus._--_Synaptotylus_ new, described below.

_Horizon._--Carboniferous.

_Diagnosis._--Sphenethmoid region partly ossified, and
consisting of basisphenoid, parasphenoid, and ethmoid
ossifications; paired basipterygoid process and paired
antotic process on basisphenoid; parasphenoid of normal
size, and closely associated with, or fused to,
basisphenoid; ethmoids paired in _Rhabdoderma_ (unknown in
_Synaptotylus_).

_Discussion._--Because of the great differences in endocranial structure
between the Devonian and Pennsylvanian coelacanths, they are here placed
in new subfamilies. The two proposed subfamilies of the family
Diplocercidae are the Diplocercinae and the Rhabdodermatinae. The
Diplocercinae include those coelacanths having two large unpaired bones
in the endocranium (at present this includes _Diplocercides_ Stensioe,
_Nesides_ Stensioe and _Euporosteus_ Jaekel). The subfamily
Rhabdodermatinae is composed of coelacanths having reduced endocranial
ossification, as described in detail above, and now including
_Rhabdoderma_ Reis and _Synaptotylus_ n. g.

Members of this subfamily differ from those of the subfamily
Diplocercinae in having several paired and unpaired elements in the
sphenethmoid region of the endocranium, instead of only one larger
ossification. They differ from those of the suborder Coelacanthoidei in
the retention of basipterygoid processes.

_Synaptotylus_ is more clos