78 Transactions. — Zoology. 



condyle {oc) moderate, reniform, flattened, and excavated above, with a mesial 

 notch, slightly excavated beneath, but not laterally. 



The foramen (^Fm) is veiy 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 mai-gins almost straight. The 

 occipital area is rather square in form, with a blunt mesial ridge {So), having a 

 shallow pit (a) on either side, but no fontanelles. A bold par-occipital process {2^0) 

 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 (h) 

 separates this process from the basi-occipital, which is very largely developed, 

 and has two inferior lateral processes (l) separated by a wide, smooth, sub- 

 condylar notch (c), and then extends forward as a broad, slightly-concave 

 surface, which occupies a large area at the base of the skull (hr). The basi- 

 sphenoid [Bs) has a small shai-e in the base of the skull, and has large oval 

 basi-pterygoid facets (6/>) only slightly divergent. 



The character presented by the tympanic fossa is very remarkable, as it is 

 divided into a posterior and anterior portion by a quadrate ossicle (ms) that 

 connects the tip of the mastoid process with the basi-occipital and with the 

 anterior process of the ex-occipital, thus enclosing a wide canal descending 

 obliquely backwards and outwards, with a sub-circular aperture deeply notched 

 inferiorly. The articular portion of the tympanic fossa, with its two facets, 

 is thus separated from the posterior or auricular portion, a character which 

 appears to be unique.*' 



The frontal bone {F) is slightly swollen at the vertex and depressed between 

 the orbits, which have strong overhanging orbital processes, on which are rough, 

 dee})ly-impressed areas (cZ), which probably gave attachment to a posterior 

 development of the cere of the mandible, these impressions being separated 

 by a smooth groove with only a faint mesial ridge. There appears to have been 

 a deep notch (df) in the upper part of the orbital border, but the lachrymal bones 

 having been lost this is not very clear. The width of the nasal suture {Fn) 

 is equal to the length of that for the attachment of the lachrymals {Fl), which 

 extends from the glandular groove to the transverse suture. The inter- 

 orbital septum is complete, and there are well-ossified rhinal chambers {Eh). 

 The roof of the orbit is flat, and with a very slight granular groove. The 

 optic foramen is at the posterior and inner angle of the orbit, directly above 

 the front of the basi-pterygoid facet. Behind the post-orbital process is a deep 

 imperforate pit. The brain cavity extends for 6 lines anterior to the optic 

 foramen. The upper mandible has all its elements completely fused ; the 

 large nostrils {e) occupy more than half of the superior sloping area, their 

 * I have since found it, but less marked, in Cereopsi^. 



