OCR Text |
Show 372 DR. ST. GEORGE MIVART ON THE SKELETON OF [May 7, while its outer margin continues on as the apex of the whole sphenotic process (fig. 7, sph, p. 378). The external margin of that whole process, in P. erithacus, is even; no marked process projecting from it outwards and ventrad in front of the ascending process of the quadrate. In L. flavopalliatus the sphenotic process curves a little inwards towards its apex, is flattened externally and dorsally, and ventrally grooved antero-posteriorly. Both the groove and the process from its internal margin are, however, relatively as well as absolutely shorter than in P. erithacus-especially the process. A marked difference between the two also exists at its outer border, which, in L. flavopalliatus, sends outwards and downwards a marked ecto-sphenotic process, so that the margin of the articular concavity for the quadrate (which appears, in both species, at the hinder end of the external border of the sphenotic process), instead of being slightly marked with no definite anterior boundary, as in P. erithacus, appears very marked and is sharply limited anteriorly by the ecto-sphenotic projection (see, in fig. 1, the small process projecting downwards just in front of the summit of the ascending process of the quadrate). In P. erithacus a shallow temporal fossa runs postaxiad and slightly dorsad between the postorbital and sphenotic processes, being bounded preaxially by a marked ridge which descends on the cranial surface from the postorbital process to the inner side of the root of the sphenotic process. The temporal fossa has its dorsal margin defined by a slight ridge, very convex dorsad, which runs postaxiad from the postorbital process. The fossa is limited ventrally by another slightly marked ridge, nearly straight, or only most slightly convex dorsad, which continues on postaxiad the ventral margin of the sphenotic process. These two slightly marked ridges meet at a point as much behind tbe hinder margin of the auditory meatus as that meatus is broad, and at a little higher level than the uppermost margin of the meatus. At the point where these ridges meet there is a slight prominence which may be distinguished as the postsquamosal prominence (psp). The auditory opening iu P. erithacus is limited in front only by the ascending process of the quadrate. Its postaxial margin is formed by the anterior edge of the broad postmeatal bony lamella, which edge, or margin, is faintly concave preaxiad at its lower part, but most strongly concave preaxiad at its more dorsal portion. The meatal opening is bounded above by a narrow bony lamina which extends preaxiad and mesiad (ventrally to the outer margin of the root of the sphenotic process) to bound posteriorly the cup into which tbe outer articular surface of the head of the ascending process of the quadrate fits. The inner anterior end of the lamina hardly descends at all behind the process of the quadrate, but a marked though short process projects outwards from its middle just above the middle of the auditory opening, which prominence may be distinguished as the suprameatal process (sm). |