PROFESSOR OWEN ON CNEMIORNIS. 255 



more like it than is that of Cereo])sis (ib. fig. 7). It resembles more the latter 

 Anserine in its complex ossification. Cnemiomis differs from both those genera and 

 most other Anserines in the greater breadth of the cerebellar prominence (ib. 3) 

 along the middle of the superoccipital tract, and in its greater slope forward as it rises 

 from the foramen magnum (compare fig. 1, 3, with fig. 6, 3, PL XXXV.). A narrow 

 mesial tract slightly projects from the convex prominence in Cnemiomis ; it answers to 

 the sharper ridge (s) in Cereopsis (ib. fig. 7, s). The foramen magnum has a rela- 

 tively longer vertical diameter in Cnemiomis than in Cereopsis or Tachyeres. In the 

 vertical extent of the basioccipital ', beneath the condyle (ib. fig. 7), Cereopsis comes 

 nearer to Cnemiomis than does Tachyeres. A greater proportion of the parieto-frontal 

 expansion of the cranium appears in the direct back view of the skull in Cereopsis than 

 in Cnemiomis — the bi-ain being smaller relatively, and the muscular impressions more 

 extensive, in the larger extinct Anserine. 



The extent of the insertion of the portion of the "longus colli posticus" (Zool. 

 Trans, iii. p. 283, pi. 32. o**), impressing the sides of the cerebellar protuberance, and 

 leaving a convex ridge on each side the mid tract, dividing the occipital from the 

 parietal surface, gives greater breadth to the upper part of the occiput, so defined, in 

 Cnemiomis than in Cereopsis ; the insertions of the " complexus " {tom. cit. ib. y) leave 

 the deeper impressions (PI. XXXV. fig. 'i,y y) bounded by the lateral ridges; and these 

 are more distinct from the " biventer " impressions than in Cereopsis. 



The basioccipital protuberances (ib. figs. 2, 4, v) are more developed than in any 

 known Anserine, though they are well marked in Cereopsis (ib. fig. 7, r) and indicate 

 great size and power of the " recti capitis laterales " muscles (Zool. Trans, iii. p. 286, 

 pi. 32. d). In the deep chink-like fossa between the protuberances and the paroccipitals 

 open the canals giving passage to the hypoglossal and vagal (fig. 2, v) nerves and the 

 paroccipital foramen (ib. p) (perforating the base of the paroccipital and opening into 

 the tympanic cavity). The paroccipitals (figs. 1-4, 4), giving insertion to the " trachelo- 

 paroccipitales " (Trans. Zool. Soc. iii. pi. 34, fig. 1, s), are subcompressed, and do not 

 descend below the basioccipital protuberances. 



The basisphenoidal fossa (PI. XXXV. figs. 4 & 9, 5), the floor of which is formed by 

 a short triangular lamelliform process, receives on each side a (vascular X) canal from 

 the tympanic cavity. On each side of the fore part of this fossa the entocarotid canals 

 (ib. ib. e c) are exposed in Cnemiomis, which converge to terminate at the back part 

 of the deep " sella." Of these canals there is only a minute indication in Cereopsis. 

 In advance of them the basisphenoid contracts and develops the pair of pterapophyses 

 (ib. ib. 5'), here, as in other Anserines, well marked, but sessile ; they are a long ellipse 

 in shape. 



The base of the alisphenoid swells out, external to the entocarotid opening, to 



' The " fontancUes " " due to original arrest of ossification between the exoooipital aud mastoid " (Anat. of 

 Yertehrates, tom. ii. p. 49), are obliterated in both Cnemiomis and Cereopsis. 



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