No. 3] THE OSTEOLOGY OF THE PIGEONS. 491 



foramen, giving exit in life to the optic nerves, but not so with 

 the equally extensive aperture above for the nerves of the first 

 pair. So much for these interorbital fenestrae. At the upper 

 part of an orbit the groove for the olfactory nerve is seen to 

 be single, and anteriorly it enters a very small circumscribed 

 foramen above the pars plana. The pars plana and the very 

 large lacryntal bone fuse completely together, and to some 

 extent with the frontal bone above them. This creates an 

 unusually broad, entire inter-orbito-narial partition. Upon its 

 outer border the lacrymal is broadly notched ; below it meets 

 the zygomatic bar, and in front it is seen to be wedged in 

 between the nasal and frontal, this wedge being another con- 

 siderable part of the bone. In the cranium of this Passenger 

 pigeon the tyjnpanic cavities are large, very open and exposed, 

 and either one of them facing downwards, forwards, and 

 upwards. The anterior apex of the basitemporal gives but 

 slight protection to the mesial common aperture of the Eusta- 

 chian tubes. Close to and upon either side of this opening 

 we are to note an aborted basipterygoid process, and neither of 

 these latter meet the pterygoid bone opposite them.^ 



The rostrum in this pigeon is thickened, rounded below, and 

 gradually tapers to a sharp point anteriorly, being fused in the 

 latter locality with the lower margin of the mesethmoid, which 

 here extends forwards considerably beyond the pars plana upon 

 either hand. The Passenger pigeon has no vomer, and Parker, 

 in his Morphology of the Skull, says, " In the Pigeons and Sand 

 grouse the vomer is absent" (p. 263); but T. J. Parker, in his 

 Zootomy, declares for Coliimba livia that "the vomer [is] a 

 small median bone lying between the palatines at the anterior 

 end of the parasphenoid." Perhaps the vomer is sometimes 

 present and sometimes absent, and I am inclined to think that 

 this may apply also to some of the Tetraojiidce, as declared 

 by me in a former memoir. 



1 This fact rather surprises me, as heretofore I have always been under the 

 impression that the basipterygoid processes among the Columbid(Z were fully 

 functional, and extensively articulated with the pterygoids. Not so, however, in 

 this specimen (No. 18520, Coll. U. S. Nat. Mus.). It will be interesting to 

 examine more specimens of Ectopistes on this point. 



