[59] 



THE OSTEOLOGY OF AMIA CALVA. 



805^ 



of the frontal. Above each one we observe a canal for the passage of 

 the olfactory nerve from the brain-case to the nasal capsule. The exit, 

 for the trigeminal nerve is bridged across by a thin lamina of bone,, 

 apparently -aftbrded by the prootic. Another and smaller osseous bridge 

 is found immediately" to the rear of this first one. Upon this view the 

 suture between the ex- and basioccipital is plainly visible, while a deep 

 concavity exists in the region through which it is directed. 



The parasjiJienoid (Fig. 27, Fr. 8.), prefrontal, and vomer may also be^^ 

 studied from a lateral view, and the hasisphenoid is likewise brought^ 

 into sight. {B. S.) 



A rear view of the cranium presents most conspicuously among its , 

 points for examination the circular and conically concave facet for ar- 

 ticulation with the centrum of the atlas. It is developed by the basi- 

 occipital and somewhat lower in position .than the horizontal i^laue ^ 

 of the parasphenoid. Above it are two elliptical facets, directed down- 

 wards, backwards, and inwards, for articulation with similar surfaces 

 on the first verterbra. Between these exoccipital facets and yet well . 

 above them is the foramen magnum, a heart-shaped opening looking 

 downward and backward. The suture dividing the exoccipitals is, 

 plainly visible in the median plane of its inferior circumference. 



Just above the exoccipital facet, on either side, we find the vagus; 

 foramen for the exit of that nerve. Anterior, and at the same time in- 

 ternal to these openings, is to be found a shallow facet, one on each'. 

 side. These are for the heads of a jjair of occipital rihs that articulate 

 at these points, and which I have elsewhere described.^^ 



The exoccipitals meet just above the foramen magnum, at which point, 

 they receive between them the thin lamelliform crest of the supraocci- 



ep,.a 



6-^Shufel(lt, R. W. " Osteol- 

 ogy of the large-mouthed Black 

 Bass." Science, No. 65. Cam- 

 bridge, May 2, 1884, p. 532- 

 These ribs are of so much in- 

 terest and at the same time sa> 

 much importauce from a mor- 

 phological point of view, that 

 I feel warranted in reproduci«g; 



my original figure of them irb 



Left lateral view of cranium of Jl/tcropte/MS saZjwoides^ showing i-r- p , <.„ ,-ii„„4.„„j.- _ i^ j. 



..,,., ^ „ ,„ . ,.,.., . „ this ioot-uote,illustrating what, 



occipital ribs, Oc. r. Half size of the original specimen; from • i i • i, 



author's drawing published in Science (No. 65.) S. eth, supraeth- ^ '^^^^ ^'*''" above in the text., 

 moid : vg. vagus foramen ; and the other lettering the same as As already announced in i>ci — 

 figures in this paper. ence, I have since detected thcmi, 



in the Tunny (0. Thyimus) and suspect their occurrence in some of the Scombridfe*,. 

 It will be interesting for those now engaged in dissecting fishes, or others investigat- 

 ing the anatomy of the class, to be on the lookout for these structures. The family 

 Centrarchidse should receive particular attention in this regard, and of these the> 

 genus Lepomia stands among the first to be suspected. Their exact location and con- 

 stancy should be noted. 



