| OCR Text |
Show 1873.] DR. J. HECTOR ON CNEMIORNIS CALCITRANS. 765 mobility of the upper mandible, which in such birds is usually effected by the flexibility of the thin nasal bones, must, if it existed, have been effected by a straight joint with thick irregular margins, somewhat as in the Parrot. In the occipital region the muscular ridges are moderately developed. The condyle (1) moderate, reniform, flattened, and excavated, with a mesial notch above, slightly excavated beneath, but not laterally. The foramen is very large, being one third the height of the occiput in its vertical diameter, which is one fourth greater than the transverse. It is rounded above, but has the lateral and inferior margins almost straight. The occipital area is rather square in form, with a blunt mesial ridge, having a shallow pit on either side, but no fontanelles. A bold paroccipital process (4) extends downwards and backwards on each side, and forms the extremity of the cranium in that direction, giving rise to the most remarkable feature in its external conformation as viewed laterally. A deep perforated pit separates this process from the basioccipital, which is very largely developed, and has two inferior lateral processes separated by a wide, smooth, subcondyloid notch, and then extends forwards as a broad, slightly concave surface which occupies a large area of the base of the skull (Plate L X V I I . fig. 2. 1"). The basisphenoid (5) has a small share in the base of the skull, and has large oval basipterygoid facets (5') only slightly divergent. The character presented by the tympanic fossa is very remarkable, as it is divided into a posterior and anterior orifice by a quadrate ossicle (ms.) that connects the tip of the mastoid process with the basioccipital and with the anterior process of the exoccipital, thus enclosing a wide canal descending obliquely backwards and outwards with a subcircular aperture deeply notched inferiorly. The articular portion of the cavity with its two facets is thus separated from the posterior or auricular portion-a character which appears to be unique, and the converse of the prsemastoid arch which exists in Aptornis. This is shown in the oblique perspective sketch which has been made for m e by M r . Nairn :- Side view of skull of Cnemiornis. |
