78 Transactions. —Zoology. 
condyle (oc) moderate, reniform, flattened, and excavated above, with a mesial 
notch, slightly excavated beneath, but not laterally. 
The foramen (Zm) 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 (So), having a 
shallow pit (a) on either side, but no fontanelles, A bold par-occipital process ( po) 
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 (ó) 
separates this process from the basi-occipital, which is very largely developed, 
and has two inferior lateral processes (/) 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 (br) The basi- 
sphenoid (Bs) has a small share in the base of the skull, and has large oval 
basi-pterygoid facets (bp) 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 (7) is slightly swollen at the vertex and depressed between 
the orbits, which have strong overhanging orbital processes, on which are rough, 
deeply-impressed areas (d), 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 
а deep notch (d’)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 (F'n) 
is equal to the length of that for the attachment of the lachrymals (77), which 
extends from the glandular groove to the transverse suture. The inter- 
orbital septum is complete, and there are well-ossified rhinal chambers (2h). 
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) oceupy more than half of the superior sloping area, their 
* 1 have since found it, but less marked, in Cereopsis, 
