22 



PROCEEDINGS OF THE ACADEMY OP 



two birds is produced, in great measure, by the greater developement and 

 somewbat different shape of these two bones. The discrepancies in length 

 Lave already been adverted to. Those of sbape consist chiefly in the greater 

 elevation of the apices of the inter- and infero-maxillary bones. The line 

 formed by the mandibular ramus of the intermaxillary and the malar bone, 

 is in torquatus a gentle curve, the concavity of which looks downwards ; in 

 Adamsii it is a straight, line. The commissural edge of the inferior maxillary 

 of torquatus is about straight as far as the angle of the jaw ; in Adamsii it is 

 a gentle curve, whose concavity looks upwards. The greater production of 

 the inter- and infero-maxillary bones makes their apices much more acute in 

 Adamsii than in torquatus, while, at the same time, in consequence of the 

 comparative narrowness of the skull of the former, the angle of divergence 

 of the rami of these two bones is not greater, and the bill on this account no 

 wider. The symphysis of the mandibular rami is longer in Adamsii than in 

 torquatus, and the prominence at the angle of the jaw is more marked. 



In addition to the above, it may be said, in general terms, that the various 

 ridges and depressions of the skull of Adamsii are more strongly marked 

 than those of torquatus, corresponding to the superior size and muscularity 

 of the former. The occipital protuberance and crest, the interparietal and 

 the median frontal ridge are exceedingly prominent, while at the same time, 

 the crotaphyte depression, the temporal and digastric fossae and the supra 

 orbital fossae for the lodgement of the nasal glands are deep and well defined. 

 The frontal bone of Adamsii rises more rapidly than that of torquatus, leaving 

 a deeper fossa at the fronto-maxillary suture, and also producing chiefly the 

 difference which exists in the absolute height of the two crania. 



I append the detailed comparative measurements of the most important di- 

 mensions of the skulls of the two birds, which will show at a coup d'aiil the 

 absolute and relative difference in size and shape. Notice particularly the 

 great discrepancies in the longitudinal dimensions as compared with the slight 

 difference in the several transverse measurements. 



Comparative Measurements. 



Length from apex of intermaxillary to occipital protuberance 



" " " fronto-maxillary suture- 



" " " anterior orbital process 



" " " posterior do. do. 



" " " apex of 08 lachrym 



" '< " nasal foramen 



" " " maxillo-malar suture 



" " " tympano-malar artie 



" " " apex of yomer 



" " " posterior end of palatals- 



" of inferior maxillary 



" of symphysis of inferior maxillary 



" from apex of inferior maxillary to angle of jaw 



" of nasal foramen 



Width of skull across fronto maxillary suture 



" " " anterior orbital processes 



" " " posterior do. do. - 



" " " mastoid processes 



Greatest height of skull (without lower jaw) 



' depth of inferior maxillary 



* English inches and hundredths. 



[Feb. 



