No. 2.] SHUFELDT ON NORTH AMERICAN TETRAONID^. 315 



biued bones, the centra of the two mid-cranial vertebrsB, thus constitute 

 the compound bone hasi-pre-splienoid of comparative anatomists. 



Viewed from above we discover, proceeding from before backwards, 

 in the median line, 1. The upper aspect of the apophysis just mentioned, 

 and immediately to its rear the deep "sella turcica" with the osseous 

 canals of the carotids opening into one foramen at its base ; 2. Two 

 smooth surfaces, one on either side and a little laterally, for the optic 

 chiasma to rest upon ; 3. Another surface still more posteriorly for the 

 mesencephalic fossa, being perforated by diminutive parial foramina ; 

 4. A roughened open space for the articulation, with the head of the 

 wedge-like basi-occipital. Anteriorly and at the same time laterally, 

 broad and uneven borders for the alisphenoids, with their smooth 

 groovelets of the foramen ovale, while back of these again, on either 

 posterior angle, a concave wing-like expansion, the terminations of the 

 Eustachian tubes, that add to the parietes of the entrance of the otocrane. 

 Below and superiorly, at the base of the junction of the two bones, we 

 find the carotid foramina, with a depression between them mesially, and 

 still lower down, slightly protected by an attenuated offshoot from 

 beneath, the separate apertures of the anterior and buccal entrances of 

 the Eustachian tubes. 



The remaining surface, unbroken in character, extending posteriorly, 

 goes to comT)lete the basicranii. The coaptation of the elements form- 

 ing the neural arch of the parietal vertebra is shown in Plate Y, Figs. 

 47-50, their amalgamation in the adult in Plate YI, Fig. 52. 



The entire importance of the h?emal arch of this vertebra depends 

 upon the bony support it affords the tongue, and the niche it tills in the 

 chain of problems of Philosophical Anatomy. In a tine specimen of an 

 adult Lagopus Jeucitrus, kindly i^resented me by Mr. Eobert B. McLeod, 

 then residing in Leadville, Colo., we find the following characteristics 

 presented to us for examination, and they extend with little deviation 

 to all the members of the family. The hyoid arch consists of, in the 

 specimen under consideration, seven bones. The coniiuent ceratohyals 

 and glossohyal, which latter is largely completed anteriorly by cartilage, 

 form one segment; the ceratohyals diverge from each other smartly 

 behind, and at their point of meeting afford the facette for the trans- 

 verse trochlea surface on the basi-hyal. This last bone, the second in 

 order, measures half a centimeter in length, being enlarged at both 

 extremities, flattened from above downwards, the anterior end being- 

 fashioned to fulfill the purpose already mentioned, while the posterior 

 and larger extremity presents two facettes, looking backwards and out- 

 wards, to articulate with the hypobranchial elements of the tliyro-hyals. 

 The third segment also meets this compound articulation at this point, a 

 short urohyal, it too being completed at its posterior extremity by cartil- 

 age. The hypo- and cerato-branchial elements of the thyro-hyals make 

 angles with each other and curve upwards in conformity with the basi- 

 cranii. 



