=I 
SKULL OF THE “£GITHOGNATHOUS BIRDS. 30 
As a stand-point for comparison, this typical Crane’s palate is of the utmost import- 
ance if the form next to be described is to be truly interpreted. 
2. On THE SKULL OF THE SuN-BitTeRN (EURYPYGA HELIAS). 
The familiar term for this bird might serve as a text to show how completely the 
outward observation of a bird fails, in many cases, to give a clear insight into its 
nature. And yet this is, as it were, a Bittern-Crane ; a thin partition divides it from 
the Bitterns, although it is not a desmognathous Pelargomorph, but a schizognathous 
Geranomorph. 
A thorough analysis of the trunk, and, indeed, of all the rest of its body, would be 
found to harmonize with what we see in the head. 
This bird is one of those very teaching forms which, while ascending in certain things 
above its own family, also descends in others, and shows its close affinity to simpler 
types; it is at once higher and lower than a typical Crane. In the abortion of the 
presphenoidal bar it comes close to Himantopus ; but that character also occurs in Pha- 
lacrocorax amongst the Pelecanine types. This is a rare thing in the class; for, as a 
rule, if even the orbito-sphenoids are suppressed, the presphenoid runs back from the 
upper process of the perpendicular ethmoid, partly dividing the great postorbital 
fenestra of the skull where the hemispheres and olfactory crura are tilted up and lie on 
a shelving floor, most of which is mere membrane. 
The Pluvialine birds are very apt to have this deficiency of bone, through the abor- 
tion of the orbito-sphenoids and arrest of the orbital plates of the frontals. \ Also, 
beneath, the large optic foramina are only divided from each other by a membranous 
band ; and, altogether, the huge size of the eyes, and their close packing towards the 
mid line, seem to have caused this arrest of bony growth. 
In the adult Eurypyga there is no appearance of lateral occipital fontanelles; and 
they seem to have been a mere chink in the embryo: this is at once a sign of some- 
thing either Ralline or Ardeine. The occipital condyle (Plate LIV. fig. 7, oc. ¢) is also 
largest transversely and notched as in both Gruine and Ardeine. The elegantly small 
basitemporal plate (4.¢) shows also its affinity to the Bitterns; yet it agrees in form 
with that of the Crane. As is the rule in the Geranomorphe, the basipterygoids are 
merely represented in the adult by a small ridge. The parasphenoid is rather bulky 
for so delicate a skull; and the palatines do not meet beneath it: its fore end runs 
forwards like a prow beneath the cranio-facial notch; and this projection is lodged 
in the bottom of the vomerine groove. The vomer itself (figs. 7-9, v) is perhaps the 
most elegant and attenuated of any in the entire class, although it is a double bone. 
It is much more delicate than that of the Humming-bird (Trans. Linn. Soc. ser. 2, 
Zool. vol. i. pl. 22. fig. 3), and, strange to say, agrees with its Trochilian counterpart 
VOL. X.—PART vi. No. 8.—June 1st, 1878. 2u 
