1907.] TO THE OSTEOLOGY OF BIRDS. 353 



the most exhaustive account that has yet been written. Anything 

 like completion will be impossible for very many years to come, 

 owing, largely, to the difficulty in obtaining material. Large as 

 is the British Museum collection of skeletons of these birds, 

 there are considerable gaps to fill. 



As a contribution towards our knowledge of the Passeres this 

 paper will, I trust, prove useful. I have endeavoured especially 

 to throw light on the perplexing questions of classification, but 

 with what measui"e of success time must prove. 



ii. The Skull op the Adult. 

 The Occipital Region. 



The plane of the occipital foramen is tilted backwards, owing 

 to the relatively large size of the brain-case, so as to lie almost 

 horizontally : that is to say, almost in a line with the long axis of 

 the skull. 



The supraforaminal ridge is not very well marked, in so far as 

 its extension laterad of the foramen is concerned. It generally 

 terminates on the bulla which forms the outer wall of the pos- 

 terior tympanic recess. 



A pair of small foramina may be mentioned here which admit 

 branches of the vena occiiyitalis. In Pitta, Phytotoma, Pitangits, 

 Tyrannus, Prionops, Euryceros, and Lanius, for example, these 

 foramina will be found forming the termination of a pair of 

 well-marked grooves traversing the supraoccipital immediately 

 a,bove the occipital foramen ; and extending upwards towards the 

 middle line to pass into the foramina in qviestion on either side 

 of the occipital crest. But in Artamia, Ai'tamus, Corvinella, and 

 Tylas, for instance, these foramina seem to have shifted, inasmuch 

 as they appear much lower down — immediately above the rim of 

 the occipital foramen ; while in Gynmorhina, Pityriasis, Dicruriis, 

 and Vireolanias they are found on the fi-ee edge of the rim itself. 



A cerebellar dome is nowhere very well developed : it is 

 practically absent except among the Tyrannidse and Artamidse. 



The lambdoidal ridge is generally moderately well developed ; 

 though in no case is it so strongly marked as in Pitta among 

 the Tyranni, and in Lalage and Gh^aiicalus representing the 

 Campophagidfe ; it forms, however, only a very inconspicuous 

 feature of this region of the skull. 



The Cranial ^00/ (text-fig. 101). — Save only in the Tyrannidfe, 

 the cerebral dome is broad and well-rounded, while the contour 

 of the cerebrum is plainly indicated, and the interorbital region 

 of the frontal is wide. In this last character it would seem that 

 the Oampophagidfe, Prionopidaj, and Laniinte differ, in that tliis 

 region is narrow. Paradisea is peculiar in having a relatively 

 long and narrow cranium, but with the cerebral dome well 

 marked. In the Tyrannidfe the cerebral dome is conspicuously 

 depressed, but wide ; the interorbital region is generally wide in 



