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 occi- 

 put 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, 

 slio-htly concave surface which occupies a large area of the base of the 

 skull (Plate LXVII. tig. 2. 1"). The basisphenoid (5) has a small 

 share in the base of the skull, and has large oval basipterygoid facets 

 (5 f ) 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 out- 

 wards with a subcircular aperture deeply notched infenorly. 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 praemastoid arch which exists in 

 Aptornis. This is shown in the oblique perspective sketch which 

 has been made for me by Mr. Nairn :— 



Side view of skull of Cnemiornis. 



