OCR Text |
Show 1903.] OSTEOLOGY OF THE CUCULIFORMES. 259 the palatines are cut away so as to expose the parasphenoidal rostrum. The Occipital Region. The plane of the occipital foramen slopes obliquely backwards; the orifice is either reniform or cordiform. In the obliquity of this foramen the Cuculiform skull differs conspicuously from many Coraciiform skulls wherein the foramen looks directly downwards, its vertical axis lying parallel with the long axis of the skull. The supra-foraminal ridge is but ill-defined, but can be indistinctly traced running downwards, on either side, into the processus alae occipitalis. The lambdoidal ridge in the Cuculi is generally well-defined and bluntly conical in outline. In some genera, e. g. Crotophaga, Centropies, Guira, Rhopodytes, Rhinococcyx, and Saurothera, its extremities bifurcate, sending forward an anterior band across the inferior border of the squamosal to terminate in a pointed squamosal prominence overhanging the quadrate; and a posterior branch, which turns downwards and backwards to disappear on the free edge of the lateral occipital. Where the lambdoidal ridge is well-developed, the cranial roof, lying immediately in front, is more or less flattened, often, indeed, marked by deep temporal fossae. In many genera the lambdoidal ridge is much less distinct. This occurs where the cranial roof is strongly arched so as to rise above the ridge with a strong curve, and temporal fossae are wanting or confined to the sides of the cranium, e. g. Couay Gacomantis, Chrysococcyx. The supraoccipital region is marked by strong muscular depressions, which in the case of Coua, for example, take the form of widely-separated oval scars, each surrounded by a swollen border; whilst in others, as in Eudynamys, these depressions are only divided in the middle line by a narrow ridge, and are bounded infero-laterally by slightly swollen bullae produced by the lateral occipitals. The lateral occipital wing is produced downwards on either side into a small or medium-sized processus alee exoccipitalis inferior (paroccipital process). In the Musophagi the lambdoidal ridge is fairly well-defined in Schizorhis, but only very imperfectly so in Turacus. The ridge in Schizorhis is formed by the scooping-out, so to speak, of the supraoccipital to afford depressions for the insertion of the cervical muscles. On either side, and inferior to these depressions, are two rather conspicuous bullae lodging the posterior and horizontal semicircular canals of the ear. The distal ends of the lambdoidal ridge terminate before reaching the free edge of the lateral occipital wing. The j^'ocessus alee exoccipitalis inferior is only feebly developed. The lateral or exoccipital wings are not greatly developed in the Cuculiformes. |