CLASSIFICATION, AND PHTLOGENY OF THE DINOENITHID^. 381 



V. The ethmoidal region, lying anterior to the orbits, enclosing the olfactory chambers, 

 and produced forwards into a median vertical partition, the mesethmoid, anky- 

 losed below with the rostrum. 



vi. The cranial cavity. 



1. The occipital region. (Plate LVIII. fig. 9; Plate LIX. fig. 14; Plate LXII. 

 figs. 47-58.) 



The occipital condyle [oc. con.) is distinguished by its more or less pedunculate 

 character; its dorsal surface is usually somewhat flattened, and its hemispherical 

 posterior face often presents a well-marked dimple-like depression indicating the 

 position of the notochord. Its median portion is formed by the basioccipital, its 

 lateral portions by the exoccipitals (fig. 14) ; the latter bones converge from below 

 upwards, so that a very narrow strip of the dorsal surface of the condyle is furnished 

 by the basioccipital (fig. 15). 



The occipital foramen varies in form from subcircular to squarish ; in Dinornis the 

 plane of the foramen is nearly at right angles to that of the basitemporal platform, 

 while in the other genera it is distinctly inclined backwards ; in the former case the 

 occipital condyle projects beyond the dorsal margin of the foramen, a unique peculiarity 

 pointed out by Owen. In some instances the condyle projects beyond the level of the 

 paroccipital processes, but as a rule the reverse is the case. 



Immediately above the occipital foramen is a median vertical ridge (fig. 9), the 

 occipital crest (oc.cr. ; median vertical ridge, Owen), which is connected ventraUy with 

 another ridge lying immediately above the foramen, at first close to its dorsal border 

 and afterwards diverging laterad and becoming lost on the paroccipital process. I 

 propose to call this the supraforaminal ridge {swp.for.r. ; lower transverse supra- 

 occipital ridge, Owen) ; it is well developed in all the species, while the crest, although 

 usually well marked, is often obscm-e and sometimes absent in Dinornis. 



The occipital crest passes anteriorly into a transverse ridge which extends laterally 

 on each side to the base of the paroccipital process ; the median portion of this 

 lamhdoidal ridge {lamb.r. ; transverse occipital ridge, Owen) is frequently double 

 (figs. 1, 9, & 12), a transversely elongated lozenge-shaped area being enclosed between 

 its two divisions; we may thus distinguish an anterior lamhdoidal ridge [ant.lamh.r.], 

 which is dentated and serves as the chief line of insertion of the neck-muscles, from a 

 posterior lamhdoidal ridge {post. lamb.r.). The distinction between the two varies 

 o^reatly in different species, being best marked in Anomalopteryx, and hardly distin- 

 guishable in Dinornis (Plate LXI. figs. 25-34). On each side of the occipital crest, 

 close to its junction with the posterior lamhdoidal ridge, is a more or less well-marked 

 depression, the supraoccipital fossa (fig. 9, s.oc.fos.). 



The precise relation of the lamhdoidal suture to the ridges of the same name is 

 difficult to make out, as the ridges are obscure in young specimens, but it appears to be 

 a little in front of the posterior ridge. 



VOL. XIII. — p.\KT XI. No. 2. — October, 1895. 3 i 



