6 Watson & Day, Notes on some Palceozoic Fishes. 



is preserved to us this bone does not reach back to the 

 pre-operculum and the quadrato-jugal but leaves a small 

 irregular opening in the long cheek, which may perhaps, 

 but very improbably, be original, but is more likely to 

 have been closed by a separate element of which indeed 

 some traces seem to be visible in a single specimen. The 

 maxilla is a long somewhat shallow bone lying entirely 

 in the skin and extending from the premaxilla to the 

 quadrato-jugal. It overlaps all bones which lie above it, 

 and its lower margin is tooth-bearing. The anterior 

 border of the orbit is surrounded by a bone or bones of 

 which we can say nothing. 



Fitting into the gap between the squamosal and 

 tabular is a small quadrate bone whose lower and pos- 

 terior margin is connected with the upper border of the 

 large operculum. This element fits closely up to the 

 tabular and its posterior edge is rounded. It overlaps 

 the sub-operculum below it, whose anterior border fits the 

 pre-operculum. The remainder of the opercular appa- 

 ratus is not well shown in the Manchester specimens, but 

 the sub-operculum supports the posterior of the lateral 

 gulars, which themselves articulate with the paired prin- 

 cipal gulars. 



Articulated with the inner sides of the tabulars are 

 distinct post-temporals, thin dermal bones with a great 

 resemblance to scales. These support slender triangular, 

 supra-clavicles which themselves pass under the upper ends 

 of the powerful clavicles, great sickle-shaped bones with a 

 wide exposure on the whole flank of the fish behind the 

 opercular apparatus. The lower ends of these bones over- 

 lap the upper ends of the infra-clavicles which are them- 

 selves triangular bones on the ventral surface of the fish 

 filling up the notch between the posterior margins of the 

 principal gulars. From the outer corner of each 



