1901.] SHUFELDT — OSTEOLOGY OF THE CUCKOOS. 33 



partition aided by the large, descending part of the lacrymal forms 

 a very efficient bulwark between the orbit and the rhinal chamber ; 

 while, laterally, in front of the last mentioned bone quite a sizable 

 vacuity exists ere arriving at the posterior edge of the nasal. 



The base of this vacuity is spanned by the slender maxillary. 

 Either aural entrance is capacious, and underspanned by a fairly 

 well-developed tympanic bulla. A side of the osseous superior 

 mandible is flat and nearly smooth, being only slightly scarred by 

 delicate vascular venations. Passing next to the base of this skull 

 we find the basitemporal region smooth and rather contracted, the 

 tympanic bulla dipping down considerably below it upon either 

 hand. A pointed bony shield underlaps the anterior entrance to 

 the Eustachian tubes, and the foraminal apertures for the hypo- 

 glossal and vagus nerves, and the carotids are very small and incon- 

 spicuous. The lower border of the sphenoidal rostrum is narrow 

 and rounded, while either pterygoid is somewhat short, straight and 

 characterized by a raised and sharpened superior border for its an- 

 terior two-thirds. These bones articulate far forward from the 

 cranial base, and no sign whatever is seen of basipterygoidal pro- 

 cesses. 



For their r major part the palatines lie in the horizontal plane, 

 they being for their lengths nearly of uniform width, and their 

 postero-external angles are very much and completely rounded off. 

 They are in contact along the middle line next the rostrum but do 

 not seem to fuse together there, and their supero-mesial margins 

 are produced forward into a single and diminutive spicula of bone, 

 which possibly represent the vomer. Crotophaga is desmognathous 

 by the fusion of its delicate and spongy maxillo-palatines across the 

 middle line. Indistinguishably fused with these seems to be an 

 osseous septum narium, and the spongy osseous tissue that fills in 

 the hinder moiety of the cavity of the upper mandible. The 

 prepalatine portions of the palatines are in intimate contact with 

 the maxillo-palatines, while anteriorly these horizontal plates be- 

 come continuous with the flat bony roof of the nether surface of the 

 osseous beak ; quite as we fine them in all of our Cucididcz. 



With respect to the mandible, we find it of the V-shaped pattern, 

 with a moderately deep symphysis, the latter being concaved above 

 and roundly sharpened along the median line below. The ramal 

 sides are of nearly uniform depth throughout and are by no means 

 narrow ; the interangular vacuity behind being small (PL II, Fig. 8). 



PROC. AMEK PHILOS. SOC. XL. 165. C PRINTED JUNE 1, 1901. 



