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Show 1 9 0 3 .] OSTEOLOGY OF THE CUCULIFORMES. 2 7 1 Internally the squamosal appears to he visible only in Cuculus canorus and Centropus, where it appears as a small triangular plate wedged in between the prootic, parietal, and alisphenoid. The nasal, judging from the scanty material at my disposal, differs slightly in form in different genera, inasmuch as in Cuculus and Centropus it is not sufficiently large caudad to cover the horizontal plate of the mesethmoid. In Centropus the hinder border is produced into a sharp angle, and is rounded in Cuculus and Geococcyx. The nostril is holorhinal. The lachrymal offers 110 special features for comment. The premaxilla is fully ossified only in the skull of Geococcyx. Its nasal processes are long and slender, and the median suture dividing them extends far beyond the level of the anterior border of the nasal fossa. The maxillary and palatine processes lie close together and parallel with one another. The maxilla in Geococcyx is elongated and triangular in form, and sends backwards from its postero-external angle a long slender bar to join the jugal and quadrato-jugal. The body of the maxilla is slightly spongy and has the postero-internal angle produced backwards and inwards into a maxillo-palatine process. The body of the maxilla lodges a barely perceptible antrum. The quadrato-jugal is long and slender in Geococcyx ; the relations between the jugal and maxilla cannot be made out, the skull having become disarticulated. The vomer is absent. The palatine does not differ appreciably from that of the adult. The pterygoid is rod-shaped, and produced forwards into a sharp triangular spine (PI. X X II. fig. 10), which articulates with a corresponding facet in the mesial border of the palatine. Later this triangular process becomes segmented off from the main shaft to form the hemipterygoid, which ultimately fuses with the palatine. At the present stage this segmentation is faintly indicated by a shallow furrow on the outer surface of the shaft. In the adult, where the fusion with the hemipterygoid is complete, the palato-pterygoid articulation is formed by the approximation of glenoid surfaces sloping obliquely backwards. The dentary and splenial do not differ from those of the adult. The coronoid, angulare, and supra-angtdare are all as yet distinct. iv . T he V e r t eb r a l C o lum n . The vertebral column of the Cuculiformes is not marked by the same constancy of character which is so conspicuous in the skull. In many respects it recalls that of the Coraciiformes, but even among the Cuculi relatively wide differences obtain. All the presynsacral vertebrae are heteroccelous, and all the thoracic vertebrae are free. The cervicals of the smaller Cuculi recall those of Leptosoma. The odontoid ligament of the atlas is ossified. The axis vertebra is very short antero-posteriorly, and has the neural arches produced P roc. Z ool. Soc.- 1903, V ol. I. No. XV III. 18 |
