472 
ME. W. K. PARKER ON THE DEVELOPMENT 
wide. The ethmo-nasals ( et.n) are less, and the frontals (f.) are larger; the palatine 
is gone, and the pterygoid ( pg) is becoming a much thicker bone. Over the coronoid 
process ( cr.c .) the supra-angular bone (s.ag.) is seen, the dentary (d.) is very extensive, 
and is helping the supra-angulare to cover the coronoid cartilage, and growing down the 
outside of and coming beneath the main rod (mk) The coronoid bone (under cr.c.) 
now appears inside the mandible. 
Section 8.—This slice (Plate 35, fig. 5) is a little in front of the hinge of the lower 
jaw, and behind the outspread wings of the trabeculse ; hence, the rostrum appears 
to be single, although it has the trabeculse confluent with it in its lower half. About 
the middle there is a slight hollow ; above, it is rounded, and at its base somewhat 
mammillate in section ; this part has the parasphenoid ( pa.s.) fitting to it, which is 
thus convex instead of carinate. 
The pterygo-palatine ( p.pg) is oblique and oval; it is nearer the rostrum than the 
mandible; that part ( cir.c.) is larger than the rostrum, and is irregularly spindle-shaped 
in section, with its upper half slightly incurved ; in its inner face the “articular” centre 
(ar.) has appeared. The basi-hyal ( b.hy.) is now wider, and thicker; flat above, and 
convex behind. The ethmo-nasal bone (et.n.) is narrower, and the frontal (f.) wider; 
the parasphenoid (pa.s.) has lost its keel, and become convex and alate. The pterygoid 
( pg.) has now more diploe above, is growing far down as a thin lamina inside the angle 
of the mouth; the dentary (d.) lies on both sides of the lower half of the cartilage ; 
above, the supra-angulare (s.ag.) lies over it, and below, the angulare (ag.) flanks it. 
Section 9.—A little further back (Plate 35, fig. 6) we get a similar section to the last, 
but the pterygoid (below p.pg) is still more complex, above, and the articular cavity 
of the hinge of the lower jaw (g.c., ar.c.) is laid open, and has a piece of the quadrate 
in its hinder face. 
Section 10.—This is through the fore part of the eye-ball (Plate 35, fig. 7, e.) ; and 
here, the upper part of the chondrocranial mass is thicker; for it is in the ethmoidal 
region, and the olfactory nerves (T.) now run through tunnels in the closed-in skull. At 
this part the suspensorium is cut through in the quadrate region (g.c); it appears as 
a sigmoid tract; thin above, thicker and rounded below, and with its upper, slightly 
out-turned, edge not far from the cranial axis. Below, the basi-hyal (b.hy.) is becoming 
more solid. Here each frontal is mainly a flat lamina, becoming complex externally; 
some of the complex outer part, however, belongs to a circumorbital. Inside the 
suspensorium the pterygoid (pg) is a sigmoid tract of diploe, and below the cartilage 
a small, triradiate tract of bone is cut through ; this is the preopercular (p.op.). 
Section 11.—Here (Plate 35, fig. 8) the cranium is cut through where the olfactory 
lobes (C 16 .) lie ; it is therefore behind the proper septal portion of the intertrabecula, 
and shows the beginning of the tegmen cranii (t.cr.). The other parts are similar to 
those exposed in the last section, but, here, the quadrate bone (g.c) is seen in the lower 
part of the suspensorium, as an enclosing ectosteal plate. 
Section 12.—A little further back (Plate 35, fig. 9) the section is through the 
