1889.] MR. W. K. PARKER GN STEATORNIS CARIPENSIS, 165 
turn,” 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 line, is 29 millim. long; the skull 37°5 millim. 
In the skull of a smaller, but older, specimen the measurements 
are, rostrum 27 millim., skull 35 millim. The bony rostrum 
(Plate XVII. fig. 1) in both cases is deflected 8 millim. below the 
general palatal plane ; this is seen toa much greater extent when the 
horny covering is on. Therefore, there is in this case, still more 
than in Oorythaiz, and other Cuculines with a decurved beak, a 
quasi-Raptorial appearance. Indeed, the skull of Steatornis is 
very much like that of the Ceylon Owl (Ketupa ceylonensis); a 
likeness 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 :— 
millim 
Length of rostrum s.2ia ¢ res. yey 27 
Length of skull, proper... .................. 35 
Width of fronto-nasal hinge .. .. nek we 11 
Width of narrowest part of frontal region ' 12°5 
Width across postorbitals .............. oweee o4 
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 equal. 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 millim. long, 
16 millim. 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 Coceygomorphine 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 1 cannot imagine ; see his 
remarks in the otherwise unassailable and excellent article “ Ornithology,” 
Encyel, Brit. 9th edit. yol. xviii. p- 471. 
Proc. Zoou. Soc.—1889, No. XII. 12 
