1889.] MR. W. K. PARKER ON StEATORNIS CARIPENSIS. 165 



turnae," cannot be improved. Why they should now stand midway 

 between Swifts and Cuckoos must be determined by those who have 

 the power of reading and interpreting the hard sentences of Nature. 

 Bearing all these difficulties in mind, we may now look into the 

 details of the supposed ancestral form of the Goatsucker type. 



II. The Skull. 



In a large, but evidently rather young, specimen the " rostrum," 

 measured in a straight Hue, is 29 miilim. long ; the skull 3 7'. 5 milhm. 

 In the skull of a smaller, but older, specimen the measurements 

 are, rostrum 27 miUim., skull 35 miilim. The bony rostrum 

 (Plate XVII. fig. 1) in both cases is deflected 8 miilim. below the 

 general palatal plane ; this is seen to a much greater extent when the 

 horny covering is on. Therefore, there is in this case, still more 

 than in Corythaix, and other Cuculines with a decurved beak, a 

 quasi-Raptorial appearance. Indeed, the skull of Steatornis is 

 very nmch like that of the Ceylon Owl {Ketupa ceylonensis) ; a 

 Hkeness which is intensified by a similar development of the " basi- 

 pterygoids " in both cases. I believe that this is mere isomorphism. 

 The measurements of the lesser skull are as follows : — 



miilim. 



Length of rostrum 27 



Length of skull, proper 35 



Width of fronto-nasal hinge 11 



Width of narrowest part of frontal region ' .... 12*5 



Width across postorbitals 34 



Width across occipital wings 31 



Width across quadrato-jugal hinges 35 



Thus we see that the length and the greatest breadth of the skull, 

 proper, are equid. This at once stamps the skull with an Owl-like 

 character, which is intensified by the narrowness of the upper inter- 

 orbital tract, the large size of the very open orbits (19 miilim. long, 

 16 milhm. deep), and the form of the upper beak, or " rostrum," 

 Put side by side with the skull of Ketupa ceylonensis, it seems as 

 if it must belong to an allied genus, at least ; but in the details of 

 its structure it is soon found to be Cuculine. 



The skull of the Ceylon Owl and that of its Strigine congeners, like 

 that of most Diurnal Rapacious birds, is indirectly Desmognathous. 

 The skull of Steatornis, however, is doubly Desmognathous (Plate 

 XVII. fig. 3). and has its alinasals (Plate XVII. figs. 1, 2, al.n.) 

 ossified in the true Coccygomorphine fashion ; these parts remain 

 cartilaginous in the Owls". 



^ In the lesser skull this part is a little wider than in the two large specimens, 

 whilst the surface is gently concave in it, and convex in the larger specimens. 

 Are these sexual differences ? 



^ There is, I believe, but one point in Ornithology in which I am out of 

 touch with my friend Prof. Alfred Newton. Why he should doubt the near 

 kinship of the Owls to the Harriers and Hawks I cannot imagine ; see his 

 remarks in the otherwise unassailable and excellent article " Ornithology," 

 Encycl. Brit. 9th edit. vol. xviii. p. 471. 



Proc. Zool. Soc— 1889, No. XII. 12 



