Synopsis of the Families of Vertebrata. 
I. Basilar bones of median fins well de- 
veloped ; 
Scapular arch suspended to cranium ; pectoral fin 
with numerous basilar bones ; Docopteri. 
II. Basilar bones of median fins rudimental 
or wanting. Pectoral basilars few. 
A. Scapular arch suspended to the anterior vertebrae. 
Maxillary bone distirfct ; no interclavicles ; epi- 
branchials and pharyngeals present ; inferior 
elements distinct; Opsithomi. 
AA. scapular arch suspended to cranium by a posttem- 
poral bone. 
a. Ventral fins abdominal. • 
Branchial arches developed, third superior pharyn- 
geal enlarged ; gill fringes linear ; no inter- 
clavicles ; Percesoces. 
Epibranchials and superior pharyngeals reduced in 
number; interclavicles; gill-fringes linear ; Heniibranchii. 
Epibranchials and superior pharyngeals wanting; 
gill fringes in tufts ; Lophobratichii- 
(j-'t-. Ventral fins thoracic or jugular. 
i5. Anterior (spinous) dorsal fin expanded into 
transverse laminae sessile on cranium. 
Cranium normal ; branchial bones present ; Discoccphali. 
(J/5. Spinous dorsal fin not traversely expanded. 
y. Posttemporal projecting freely from skull. 
First vertebra united by suture to cranium; inter- 
calaria united behind supraoccipital ; basilar 
pectoral bones elongated ; Pedicidati. 
Posterior cephalic region normal; the anterior 
twisted so as to bring both orbits on one side ; 
inferior pharyngeals distinct Heterosomata. 
Cranium normal, premaxillaries usually coossified 
with maxillaries behind, and the dentary with 
the articular ; pharyngeal bones distinct ; Plectognathi. 
